INTRODUCTION TO ORGANIC FARMING
Agriculture has been the basic source of subsistence for man over thousands of years. It provides a livelihood to half of the worldâ€TMs population even today. According to the Food and Agricultural Organization (FAO), people in the developing world where the population increase is very rapid, may face hunger if the global food production does not rise by 50-60 per cent by the year 2000 AD. The contribution of developing countries to world agricultural production in 1975 was about 38 per cent, while that of developed countries, which account for 33 per cent of worldâ€TMs population, was 62 per cent. Only those countries, which can match the demands of the increasing population with increased production, can escape mass hunger.
In the pre-independence period, Indian agriculture was usually described as a gamble with monsoons. There used to be a great deal of uncertainty about crop prospects, as monsoons played a decisive role in determining agricultural output and their failures resulted in widespread famine and misery. In the last few years, Indian agriculture has made impressive progress and so is more resilient to the vagaries of the monsoon, although the countryâ€TMs population increased from 361 million to more than 960 million.
During this period, the size of farm holdings and the per capita availability of agricultural land have also been decreasing and they are expected to be around 1.4 and 0.14 hectares respectively, by the turn of this century (Table 1). With competing demands on land for other sectors of development, this decline is likely to aggravate further.
World population today is about 5 billion. It is projected to become 6.1 billion in the year 2000, over 8 billion by 205 and nearly 10.5 billion by the end of next century. In simple terms, the basic food production must double to maintain the status quo. Hunger must be banished from the surface of earth, as a first responsibility of any civilised society to provide sufficient food for the people who are below the poverty line. The Planning Commission has projected that Indiaâ€TMs population would reach one billion by 2001.
Indian agriculture before the green revolution
Our traditional farming systems were characterized mainly by small and marginal farmers producing food and basic animal products for their families and local village communities. Farming was highly decentralized with individual farmers deciding on the types of crops to grow depending on climate and soil conditions. These traditions consisted of methods of controlling pests and diseases, and for building soil fertility and structure in their own ingenious ways, since farming did not include the use of chemical pesticides or fertilizers. Rather, soil health and pest control were achieved using practices such as shifting cultivation, conservation, the use of animal manures and farm wastes and the introduction of legumes into crop rotations. By growing a mixture of crops in the fields, early farmers insulated themselves from total crop failure caused by weather or pest epidemics. Even, Alexander Walker, resident at Baroda in Gujarat, wrote in 1820 that green fodder was being grown throughout the year; intercropping, crop rotation, fallowing, composting and manuring were practised; all these allowed continued farming on the same land for more than 2000 years without drop in yields. Further, the crops were relatively free from pests. One of the reasons for the decline in their sustainable system of agriculture was the land revenue collected by the British. A tax of 50 percent and sometimes as much as 63 per cent revenue was collected and hence more than a third of the irrigated land went out of production. Similarly, an environmentally stable form of tree and forest conservation, which had been developed over the ages, crumbled. Even sacred groves, which were preserved since time immemorial, were turned into coffee, tea, teak wood and sugarcane plantations. Hence, from 1865 India experienced the most severe series of protracted famines in its entire history.
The Green Revolution
After the green revolution was launched in India, substantial increase in the production of food grains was achieved through the use of improved crop varieties and higher levels of inputs of fertilizers and plant protection chemicals. But it has now been realized that the increase in production was achieved at the cost of soil health and that sustainable production at higher levels is possible only by the proper use of factors, which will help to maintain the fertility of the soil. In fact, about 60 per cent of our agricultural land currently under cultivation suffers from indiscriminate use of irrigation, water and chemical fertilizers. The gravity of environmental degradation resulting from faulty agricultural practices has caused alarm among the concerned farmers, scientists and conservationists and greater viable and sustainable farming systems have become a necessity. There has been a series of seminars and policy conference on this issue. One such alternative agriculture system, which will help to overcome the problems of soil degradation and declining soil fertility, is organic farming and ecological agriculture.
Most of the growth in the food production during the green revolution period is attributed to the higher fertilizer use. The growth of the fertilizer industry in India between 1965 and 1983 has been remarkable. The per hectare consumption of NPK increases from 0.6 kg in 1950 to 50 kg by 1987-88. However, the available data show that the fertilizer consumption is largely confined to irrigate areas, which constitute only about 30 per cent of the gross cropped area. The annual fertilizer consumption is expected to raise to about 20 million tonnes by the turn of this century. This rise in fertilizer use is anticipated because:
1) N deficiency will continue to be universal in Indian soils.
2) Deficiency of P will be next in the order.
3) K will become limiting in high productive regions.
4) In at least half of the Indian soils, crops would benefit from Zn treatment.
5) S deficiency will limit the productivity in a vast majority of Indian soils.
IMPACT OF GREEN REVOLUTION ON THE ENVIRONMENT
To increase the agricultural production in the country and to meet the requirements of the expanding population, it became imperative to change the methodologies. These involved the use of high-yielding varieties and higher fertilizer dosages; increasing the irrigated area and intensive cropping; bringing large areas under one crop; growing crops in non-conventional areas; and changing the crop sequences. The green revolution followed the development of commercial agriculture in the developed countries after World War II. Chemical companies that developed highly toxic and life damaging chemicals for the purpose of warfare, decided to turn their attention on the chemical control of insects, pests and unwanted plants in the farmers fields. In addition, the production of petroleum-based fertilizers by oil companies was used to replace composts and manures. The food grain production increased dramatically as the policies of green revolution began to take effect. By the year 2000, India will need to produce 230 million tons of food grains on 140 million hectares of agricultural land in order to feed an estimated 1 billion Indians.
This achievement, though remarkable, has also coasted us dearly. Along with the increase of food grain production pesticide consumption in India also increased considerably. In 1932 nearly 200 metric tons of chemical pesticides were used, but by 1975 it was 25,000 metric tons, an astounding 375-fold increase over 30 years. It is estimated that this will touch 200,000 tons by the year 2000. Despite increasing use of pesticides, annual crop losses due to pests still amount to more than Rs.15,000 crores.
Consumption of chemical fertilizers has gone up seven times in the last 20 years, but production has only increased a miserable two-fold. While we now have enough food ourselves and are concentrating on broadening our food exports, we have apparently sadly overlooked on equitable food distribution to our hungry millions. It is quite unfair to balance our countryâ€TMs trade deficit, caused by expanding imports of petroleum-based products with food exports at the expense of making the same available for local consumption. The modern agricultural techniques such as use of synthetic fertilizers and pesticides are continuing to destroy stable traditional ecosystems and the use of high yielding varieties of crop has resulted in the elimination of thousands of traditional varieties, with the concurrent loss of genetic resources. In the past, our forefathers were consuming chemical-free foods, but now a large quantity of chemical residues getting into the food chain and toxic residues in agricultural commodities is an issue of major concern to every body.
Our major concern is to meet the internal demands of farm production without degrading the productive environment. Sustainability issues have become highly relevant even under the low input use situations. There is hardly any scope of finding new land area suitable for cultivation. Since the ability of the land to produce food is limited and the limits of production are set by soil and climatic conditions, there are critical levels of population that can be supported in perpetuity from any given land area. Any attempt to produce food in excess for the restrictions set by soil and climatic conditions will, in the long term, result in failure. Degradation of land, hunger and eventual reduction in population are the outcome of such practises. However, the application of technological innovations in the form of new seeds, fertilizers, irrigation and suitable management strategies has bailed such catastrophic predictions in the past. This underscores the tremendous potential of science and shows the possibility of meeting the demands put on our farm production systems without reducing its sustainability, through scientific research.
The progress in Indian agriculture during the last 40 years can be broadly classified under three areas; First, progress in developing the research and educational infrastructure, essential for generating and testing technologies suitable for different agro-ecological regions; secondly, a reasonably efficient input production and delivery system for the production and distribution of seeds, fertilizers and other inputs. Thirdly, evolving policies essential for stimulating higher production by small farmers and increased consumption by the rural and urban poor. Thanks to these steps growth of food production has on the whole remained above the rate of population growth. Statistics on agricultural production in India from 1960 to 1988 show that during the period (a) the gross cropped area increased marginally; (b) the area under irrigation nearly doubled; (c) the high yielding variety programme, initiated at the national level, increased to cover nearly 39 per cent of the cropped area; (d) the total food production increased from 74 million tonnes to nearly 192 million tonnes; and (e) both the fertilizer and pesticide consumption increased more than 25 times. The ratio of pesticide to fertilizer remained nearly constant at 1:100. Interestingly, the use of pesticides in the public health sector, which has higher than in the agricultural sector, became almost equal in 1970 and declined significantly thereafter. The number of pesticides used in agricultural sector has always been more diversified than in public health sector, which used only DDT, HCH and malathion.
The introduction of high-yielding varieties changed the agricultural environment leading to numerous pest problems of economic importance. Many of these were either unknown or were of minor importance in the early 1960â€TMs. Increased irrigation, higher usage of fertilizers and wide adoption of high-yielding varieties led to the resurgence of pests. The high-yielding varieties and the monoculture practices led to material changes in the pest complex. Pests and diseases such as gall midge, brown plant hopper, bacterial blight and tungro virus of rice, which were of minor importance before the green revolution, suddenly assumed major proportions; for instance, spodoptera litura on cotton, maize and tobacco; Pyrilla on wheat, maize and sorghum; apple scab and codling moth on apple and Karnal bunt on wheat increased the crop losses due to pests enormously. An important aspect of the resurgence of newer pests is the time lag between the introduction of a new variety/agronomic practice and the actual manifestation of the pest epidemic. This varies with pest and the crop. For example, in the rice bacterial wilt there was a practically no time-lag in the very first season of the introduction of Taichung Native-1 in Andhra Pradesh in 1963, when the disease broke out. In the case of the rice tungro virus, it took four to five years before the diseases manifested itself in a virulent form. It took, however, a decade for the brown plant hopper to become a major pest. Similarly, every variety of hybrid bajra, when released, was thought to be tolerant/resistant to downy mildew, but within a few years all proved to be susceptible. Since the high-yielding varieties were more prone to pests and diseases, use of pesticides increased and this brought about (a) widespread occurrence of pesticide residues in nearly every agricultural commodity; (b) increased pesticide resistance in vectors; (c) resistance to pesticides in stored grain pests which was first reported in 1971 and by 1979 six major pests of stored grain became resistant to a number of insecticides and fumigants; and (d) pesticide resistance in pests of agricultural importance becoming an important constraint in increasing productivity. This is true specially for the polyphagous pests such as Spodoptera litura (tobacco caterpillar); Plutella xylostella (diamond back moth) and Holicoverpa (Heliothis) armigera (American boll worm). It is suspected that Aphis craccivora (black aphid), a serious pest of pulses, and Lipahis erysimi (Mustard aphid) have also developed resistance to pesticides.
The ills of green revolution are stated to be:
*Reduction in natural fertility of the soil
*Destruction of soil structure, aeration and water holding capacity
*Susceptibility to soil erosion by water and wind
*Diminishing returns on inputs (the ratio of energy input to output halves every 10 years)
*Indiscriminate killing of useful insects, microorganisms and predators that naturally check excess crop damage by insect pests.
*Breeding more virulent and resistant species of insects
*Reducing genetic diversity of plant species
*Pollution with toxic chemicals from the agrochemicals and their production units
*Endangering the health of the farmers using chemicals and the workers who produce them
*Poisoning the food with highly toxic pesticide residues
*Cash crops displacing nutritious food crops
*Chemicals changing the natural taste of food
*High inputs increasing the agricultural expenses
*Increasing the farmerâ€TMs work burden and tension
*Depleting the fossil fuel resources
*Increasing the irrigation needs of the land
*Big irrigation projects often resulting in soil salinity and poor drainage
*Depleting the ground water reserves
*Lowering the drought tolerance of crops
*Appearance of â€˜difficultâ€TM weeds
*Heightening the socio-economic disparities and land holding concentration
*High input subsidies leading to inflationary spirals
*Increasing the political and bureaucratic corruption
*Destroying the local culture (commercialization and consumerization displacing self-reliance)
*Throwing financial institutions into disarray (as impoverished farmers demand write-off of loans)
*Agricultural and economic problems sparking off social and political turmoil resulting in violence.
SUSTAINABLE AGRICULTURE AND ORGANIC FARMING
The ever-growing human and animal population coupled with the decreasing per capita availability of land and water; and other associated negative impacts on the environment consequent to unplanned developmental activities, have stretched the resilience of the natural resources to a level of catastrophe. The depletion and degradation of the natural resources at an alarming rate have not only caused decline in productivity but also have generated numerous environmental concerns. The compulsion to produce more has further compounded the problems leading to un-sustainability of the agricultural production system all over the world in general, and the developing countries in particular, necessitating a paradigm shift towards a holistic ecosystem management in an integrated manner for development of eco-friendly technologies.
Intensification of agriculture, an inevitable consequence of the compulsion to produce more, has put an enormous burden on the natural resources. Rapid and uncontrolled industrialization compounded by adoption of developmental programmes without due regard to their long-term adverse impact on the environment has been continuously eroding the basic resources. Development of efficient resource management strategies is therefore crucial for sustained agricultural production. Limitation in land and water resources, increase in population, conversion of agricultural land to other uses, and persistence of hunger and malnutrition in several regions of the globe have heavily underscored the growing concern for issues related to sustainability in the agricultural production systems. Our past efforts to promote the use of fertilizers particularly of N and P have caused a clear shift in the soil fertility management characterized by over-dependence on chemical fertilizers which in many contexts was wrongly conceived as substitute to organic manure, probably due to the unavailability of the latter. This has slowly but surely resulted in a decline in soil organic matter, optimum nutrient balance and consequently deterioration of physical, chemical and biological functioning of soils in many intensively cropped areas. It, therefore, calls for reversion of present chemical based soil fertility management strategy to the one based on integrated nutrient management strategy.
The importance of micro-biological research which can create a revolution in the application of micro-biological processes into technologies for supporting sustainable agriculture and ecological harmony needs to be recognized and promoted. The increased use of a variety of agricultural chemicals viz. pesticides, fungicides, weedicides, growth regulators etc has also to be viewed in same dimensions.
In the Indian scenario, the arable land availability will be reduced to 0.087 ha per capita if population is stabilized by 2050. The biggest challenge will, therefore, to be produce more food with less land demanding more water and other inputs to feed the millions. The factors, which have been responsible to usher in green revolution, are becoming subject to criticism for their second-generation problems. There is, however, option to integrate the recommended inputs with organic manure and bio-fertilizers. Besides shrinking resource of arable land availability the water for agriculture shall be most limiting factor in the coming decades. The availability of energy and power will be other limiting factors for increased agricultural production. Thus, the key to meet these challenges lies in the integrated management of the natural resources like land (soil), water, energy and also the biodiversity, which is threatened, with extinction of some endangered species.
Characteristics of Sustainable Agriculture
*Farming system based, not commodity based
*Recycling system, minimum depletion of natural resources
*Suitable to agro-ecological region, with planning based on rural recourses at watershed/village level; group approach
*Defends technological gains already made which are environment friendly
*Makes new gains through innovative technologies, new frontiers of knowledge under close watch on their impact on environment
*Increases use efficiency of agricultural inputs through INM, IPM, seed quality, water management, energy management, efficient use of bio-diversity etc
*Involves processing, value addition and marketing network
*Identifies natural resource depleting factors and take precautionary measures against soil erosion, soil degradation, pollution of soil, water and environment, etc. through location specific technology
*Monitors changes in fragile eco-systems as early indicators of impact of new innovations
*Ensures blending of local adaptability, economic viability, social acceptability and resource conservation
*Does not damage the fabric of social-rural community
*Involves local groups and institutions in planning, monitoring and implementing processes for a close watch on sustainability
Definition of Sustainable Agriculture
In the simplest form, sustainable agriculture is defined as the practice of agriculture, which is economically, environmentally and socially viable.
Very often the terms â€œsustainable agricultureâ€ and â€œorganic farmingâ€ are seen used as synonyms. But it should be clearly understood that they are entirely different concepts though some of the attributes are common. Both are eco-friendly and resource conserving. Organic farming advocates a total ban on the use of synthetic chemicals and does not always assure economic viability and hence sustainability.
The Department of Commerce, Ministry of Commerce and Industry, Government of India has launched a National Programme for Organic Production (NPOP), in view of the greater demand for produces generated through organic farming. Standards are prescribed in line with the basic standards evolved by the International Federation of Organic Agriculture Movements (IFOAM), aligned to agriculture and climatic conditions prevailing in India. Recognizing the value of traditional practices prevalent throughout the country, the package of practices will incorporate those of use in the practices to be prescribed by the accrediting agencies. Currently, the accrediting agencies are (1) Agrl and Processed Food Products Export Development Authority, New Delhi (2) Spices Board, Cochin (3) Tea Board, Calcutta; and (4) Coffee Board, Bangalore. Inspection and Certification Agencies are identified by the Accreditation Agencies based on certain criteria.
CONCEPTS, DEFINITION AND COMPONENTS
CONCEPT AND DEFINITION
The concept of organic agriculture has been perceived differently by different people. To most of them, it implies the use of organic manures and natural methods of plant protection instead of using synthetic fertilizers and pesticides. It is regarded by some as farming involving the integrated use of fertilizers and organic manures as well as of chemicals and natural inputs for plant protection. In either case the concept has been understood only partially.
Organic agriculture has been defined differently, but the description offered by Lampkin (1990) appears to be the most comprehensive one covering all essential features. As per this description, organic agriculture is a production system, which avoids or largely excludes the use of synthetic compounded fertilizers, pesticides, growth regulators and livestock feed additives. To the maximum extent feasible, organic farming system relies on crop rotations, crop residues, animal manures, legumes, green manures, off-farming organic wastes and aspect of biological pest control to maintain soil productivity and tilth, to supply plant nutrients and to control insects, weeds and other pests. The concept of soil as living system that develops the activities of beneficial organisms is central to this definition.
Organic agriculture does not imply the simple replacement of synthetic fertilizers and other chemical inputs with organic inputs and biologically active formulations. Instead, it envisages a comprehensive management approach to improve the health of underlying productivity of the soil. In a healthy soil, the biotic and abiotic components covering organic matter including soil life, mineral particles, soil air and water exist in a stage of dynamic equilibrium and regulate the ecosystem processes in mutual harmony by complementing and supplementing each other. When the soil is in good health, the population of soil fauna and flora multiplies rapidly which, in turn, will sustain the bio-chemical process of dissolution and synthesis at a high rate. This state of soil life and the associated organic transformations will enhance the regenerative capacity of the soil and make it resilient to absorb the effects of climatic vicissitudes and occasional failures in agronomic management.
The success of organic agriculture depends to a great extent on the efficiency of agronomic management adopted to stimulate and augment the underlying productivity of the soil resource. In this context, the concept of agro-ecosystem becomes relevant. A farming system unit is treated as an agro-ecosystem when it attains the semblance of a forest ecosystem in species diversity and multiplicity. The adoption of sequence and mixed cropping models in the presence of compatible species of nitrogen fixing trees with or without the association of livestock components makes the agro-ecosystem benefit from the positive interaction and stimulated cycling mechanisms. As a consequence, the system slowly achieves self-regulation and stability. Agricultural production attained at this stage will be engaging without eroding or deteriorating the natural resource base.
As the Organic Agricultural System (OAS) derives it strength from the basic productive capacity of the soil and complimentary interaction among the components of the system, the use of chemical inputs either for soil fertility management or for plant protection is excluded. This renders the system free from the pollution problems usually associated with the use of such inputs. For achieving marked improvement in soil productivity and for sustaining optimum levels of biological production, OAS lays emphasis on appropriate cropping and farming models, ensuring on-farm diversity and nutrient cycling, conservation and use of organic/biological sources of nutrients, cultural practices conducive to the conservation of soil and water resources and natural and or biological methods of pest and disease suppression.
With an understanding of the principles of organic agriculture, a straight and simple definition to the concept can be suggested. Organic agriculture is a farming system devoid of chemical inputs, in which the biological potential of the soil and underground water resources are conserved and protected from the natural and human induced degradation or depletion by adopting suitable cropping models including agro forestry and methods of organic replenishment; besides natural and biological means are used for pest and disease management by which the soil life and beneficial interaction are stimulated and sustained. The system achieves self-regulation and stability as well as capacity to produce agricultural outputs at levels, which are profitable and enduring over time, and, at the same time, consistent with the carrying capacity of the managed agro-ecosystem.
There are also different opinions on nomenclature of organic farming. Some call it as ecofarming i.e., farming in relation to ecosystem. Others prefer the term biological farming (farming in relation to biological diversity); yet others prefer the term biodynamic farming (biologically dynamic and ecologically sound and sustainable farming) or macrobiotic agriculture (agriculture in relation to macro-fauna). Whatever be the name, the basic point is that organic farming is the farming based on natural principles, which alone are sustainable. According to Fantilanan (1990), organic farming is a matter of giving back to nature what we take from it. It is safe, inexpensive, profitable and sensible. Organic farming is not mere non-chemicalism in agriculture; it is a system of farming based on integral relationship. So, one should known the relationships among soil, water, plants, and microflora and the overall relationship between plants and animal kingdom, of which, man is the apex animal. It is the totality of these relationships, which is the backbone of organic farming.
Organic farming does not totally exclude the elements of modern agriculture. Varying agro climatic conditions do need input from the current technological advances. It is basically simple, as it abhors excessive ploughing, hoeing, weeding and application of plant protection chemicals and fertilizers. The principal elements to be considered while practising organic farming are:
1.Â Â Â Â Â Â Â Â Â Maintaining a living soil
2.Â Â Â Â Â Â Â Â Â Making available all the essential nutrients
3.Â Â Â Â Â Â Â Â Â Organic mulching for conservation, and
4.Â Â Â Â Â Â Â Â Â Attaining sustainable high yield
Agricultural practices followed in organic farming are governed by the principles of ecology and are within the ecological means. Limited experience shows that this form of natural farming is the basis for sustainable agriculture and could be highly productive. It should not be misconstrued for reversion to inefficient and less productive farming systems.
ORGANIC VS NATURAL FARMING
There is a misconception that organic farming is merely to say â€œnoâ€ to chemicalism. But apart from restricting and to the extent possible eliminating chemicals (pesticides and fertilizers), it has something else also to convey. One who understands the whole concept of organic farming will be certainly inspired by it.
ESSENTIAL CHARACTERISTICS OF ORGANIC FARMING
The most important characteristics are as follows:
1. Maximal but sustainable use of local resources
2. Minimal use of purchased inputs, only as complementary to local resources
3. Ensuring the basic biological functions of soil-water-nutrients-humus continuum
4. Maintaining a diversity of plant and animal species as a basis for ecological balance and economic stability
5. Creating an attractive overall landscape which gives satisfaction to the local people
6. Increasing crop and animal diversity in the form of polycultures, agro forestry systems, integrated crop/livestock systems, etc. to minimize risk
Organic agriculture systems are not a repudiation of the assets of modern agriculture technology; neither are they systems of simple elimination of synthetic fertilizers or pesticides. Methods in organic agriculture are less intensive in terms of synthetic and other external inputs compared to the conventional farming methods, but are much more intensive from a biological point of view. Organic agriculture systems include approaches and methods like organic, biodynamic, regenerative, nature farming and premaculture. These were developed during the last 50 years. Although there are some differences among these approaches, the common understanding is that practising organic agriculture is managing the agro-ecosystem as an autonomous system, based on the primary production capacity of the soil under the given agro-climatic conditions. Agro-ecosystem management implies treating the system, on any scale, as a living organism supporting its own vital potential for biomass and animal production, along with biological mechanisms for mineral balancing, soil improvement and pest control.
KEY PRINCIPLES OF ORGANIC AGRICULTURE SYSTEMS
Organic agriculture systems are based on three strongly interrelated principles under autonomous ecosystem management: mixed farming, crop rotation and organic cycle optimization. The common understanding of agricultural production in all types of organic agriculture is managing the production capacity of an agro-ecosystem. The process of extreme specialization propagated by the green revolution led to the destruction of mixed and diversified farming and ecological buffer systems. The function of this autonomous ecosystem management is to meet the need for food and fibres on the local ecological carrying capacity.
In organic agriculture systems, one strives for appropriate diversification, which ideally means mixed farming, or the integration of crop and livestock production on the farm. In this way, cyclic processes and interactions in the agro-ecosystem can be optimized, like using crop residues in animal husbandry and manure for crop production. Diversification of species biotypes and land use as a means to optimize the stability of the agro-ecosystem is another way to indicate the mixed farming concept. The synergistic concept among plants, animals, soil and biosphere support this idea.
Within the mixed farm setting, crop rotation takes place as the second principle of organic agriculture. Besides the classical rotation involving one crop per field per season, intercropping, mixed cropping and under sowing are other options to optimize interactions. In addition to plant functions, other important advantages such as weed suppression, reduction in soil-borne insect pests and diseases; complimentary nutrient supply, nutrient catching and soil covering can be mentioned.
Organic Cycle Optimization
Each field, farm, or region contains a given quantity of nutrients. Management should be used in such a way that optimal use is made of this finite amount. This means that nutrients should be recycled and used a number of times in different forms. Second, care should be taken that only a minimum amount of nutrients actually leave the system so that â€œimportâ€ of nutrients can be restricted. Third, the quantity of nutrients available to plants and animals can be increased within the system by activating the edaphon, resulting in increased weathering of parent material.
ORGANIC MANURES, THEIR NATURE AND CHARACTERISTICS
Organic materials are valuable by-products of farming and allied industries, derived from plant and animal sources. Organic manures which are bulky in nature but supply the plant nutrients in small quantities are termed bulky organic manures, e.g. farmyard manures, rural and town compost, night-soil, green manure, etc. whereas those containing higher percentage of major plant nutrients like nitrogen, phosphorus and potash are concentrated organic manures, e.g. oil-cakes, blood and meat-meals, fish-meal, guano, shoddy and poultry manure, etc.
This is the traditional organic manure and is most readily available to the farmers. In Western countries, it is the product of decomposition of the liquid and solid excreta of the livestock, stored in the farm along with varying amounts of straws or other litter used as bedding. Indian litter is rarely used as bedding because the straw is utilized as fodder. A portion of cattle-dung is used as fuel in rural homes. Cattle-urine is absorbed in the soil spread over the floor of the shed but no extra soil is used for effective absorption of this fraction.
On an average, well-rotted farmyard manure (FYM) contains 0.5 percent N, 0.2 percent P2O5 and 0.5 per cent K2O. Based on this analysis an average dressing of 25 tonnes per hectare of farmyard manure supplies 112kg of N, 56 kg of P2O5 and 112 kg of K2O. These quantities are not fully available to the crops in the year of application. Nitrogen is very slowacting and less than 30 per cent of it is generally available to the first crop. About 60 to 70 per cent of the phosphate and about 75 per cent of the potash become available to the immediate crop. The rest of the plant nutrients become available to the subsequent crops. This phenomenon of availability of plant nutrients to the subsequent crop is known as residual effect.
Under the tropical climatic conditions of this country, the organic matter is quickly lost and fresh applications are necessary to obtain increased yields and maintain soil fertility.
High doses of farmyard manure can be applied under intensive irrigated cropping conditions, e.g. about 25 tonnes per hectare for sugarcane, vegetables, potatoes, rice, etc. 12.5 tonnes for irrigated or rain-fed crops where the rainfall is medium to heavy (about 125 cm) and from 5 to 7 tonnes in dry areas where the rainfall is low (about 50 cm). In dry-farming areas (rainfall below 50 cm), application of 2.5 tonnes of farmyard manure per hectare gives significant increase in crop yield.
The method of application of farmyard manure generally adopted in our country is defective. Most of the cultivators unload farmyard manure in small piles in the fields and leave it as such for a month or so before it is spread and subsequently ploughed in or disced in the field. Plant nutrients are lost considerably during the exposure of the manure to sun and rains. In summer, it results in rapid drying and considerable loss of nitrogen, whereas in the rainy season the available nitrogen and a good portion of soil humus are washed away. To derive maximum benefit, the farmyard manure immediately on being carted to fields should be spread and mixed into the soil. The manure can also be applied in furrows.
Compost manures are the decayed refuse like leaves, twigs, roots, stubble, bhusa, crop residue and hedge clippings, street refuse collected in towns and villages, water hyacinth, saw-dust and bagasse. The process of decomposition is hastened by adding nitrogenous material like cow dung, night soil, urine or fertilizers. A large number of soil microorganisms feed on these wastes and convert it into well-rotted manure. The final product is known as compost.
Farmyard manure and compost possess the same characteristics. The method of application of compost is the same as that of farmyard manure.
SHEEP AND GOAT MANURE
The droppings of sheep and goats make very good manure. Panning is, therefore, a common practice of ensuring the use of sheep and goat droppings in the fields. Sheep and goat manure contains 3 percent N, 1 percent P2O5 and 2 per cent K2O.
This is rich organic manure, since liquid and solid excreta are excreted together resulting in no urine loss. Poultry manure ferments very quickly. If left exposed, it may lose up to 50 per cent of its nitrogen within 30 days.
Poultry manure can be applied to the soil directly as soon as possible. After application, it should be worked into the surface of the soil. If the droppings come from the cages or dropping pits, super phosphate may be added to these at the rate of 1kg per day, per hundred birds. This improves the fertilizing quality and helps the control of flies and odour.
The average chemical composition of the poultry manure is as under:
Oilseeds are generally rich in manurial ingredients. After oil extraction, the oil cakes are rich in nitrogen and also contain phosphorus and potash.
Cultivators apply both edible and non-edible oil cakes to the soil as manure. Edible oil cakes are more profitable as cattle feeds. As such, non-edible cakes should be used as manures.
The percentage of nitrogen ranges from 2.5 in mahua to 7.9 in decorticated safflower cakes. The P2O5 contents in oil-cakes vary from 0.8 to 3 per cent and K2O from 1.2 to 2.2 per cent.
Oil-cakes though insoluble in water are quick-acting organic manures, their nitrogen becoming quickly available to the plants in about a week or ten days after application. Mahua oil-cake, however, takes about two months to nitrify. The solvent-extracted oil-cakes are somewhat more quick-acting than the ghani-hydraulic or expeller-pressed oil-cakes. The quantity of organic matter that gets added in normal application of oil-cakes is too small to cause improvement in physical properties of soil.
Oil-cakes need to be well-powdered before application so that they can be spread evenly and are easily decomposed by micro-organisms. They can be applied a few days before sowing or as top-dressing. Mahua-cakes should, however, be applied quite in advance of sowing time. Oil-cakes are more effective in moist soil and in wet weather than in dry soil and in dry weather. In fresh condition, oil-cakes should not be put in contact with germinating seeds or young plants as they become permeated with fungi and molds in the soil.
The use of oil-cakes on food grain crops like wheat and rice is not recommended now on economic grounds. Cakes, specially ground-nut and coconut, are extensively applied for top-dressing of sugar-cane crop. Farmers growing betel leaves also use oil-cakes.
MEAL GROUP OF MANURES
These are all quick-acting manures suitable for all types of soil and for all crops. In this group come blood-meal (generally used in grape cultivation), meat-meal, fishmeal, horn-and hoof-meal and bone meal. Meat-meal and blood meal are applied like oil-cakes whereas fish-meal should preferably be powdered. Horns and hooves of slaughtered or dead animals are converted into horn and hoof-meal by cooking in the bone-digester, and then drying and powdering them.
Bone-meal. Sterilized bone-meal is an important mineral supplement in livestock feed; yet it is used chiefly as phosphatic fertilizer. Small quantities of nitrogen are also applied to the soil through bone-meal. The availability of phosphorus from bone-meal depends on the particle size; the finer the particles, the greater the phosphorus availability. It is available to farmers in two forms: (a) raw bone-meal; and (b) steamed bone-meal.
Raw bone-meal consists of crushed bones. The percentage of phosphoric acid and nitrogen varies with the quality of bones and the age of the animals from which these are obtained. Normally, the bones of grown-up animals contain more of phosphoric acid and less nitrogen than those of the young ones. According to the standards laid down by Indian Standards Institution, the raw bone-meal must pass wholly through 2.3 mm I.S. sieve of which not more than 30 per cent shall be retained on 850 micron I.S. sieve.
Steamed bone meal is obtained by treating the bones with steam under pressure and is generally preferred to raw bone meal. Steaming increases the percentage of phosphoric acid and reduces the nitrogen content of the bone meal. It also removes the fat from the bones, which makes bone meal very porous and easy to grind. Steamed bone meal also decomposes more rapidly in the soil than raw bone meal. According to I.S.I. standards, not less than 90 per cent of the material should pass through 1.18 mm I.S. sieve. Other specifications laid down by I.S.I. for the chemical composition of raw and steamed bone-meal are as under:
Bone meal is considered useful for all soils. Best results are, however, obtained on acidic soils and soils having good drainage. It is less effective on heavy clay and calcareous soils. It has particularly notable effect on soils, which are well supplied with organic matter. Paddy, wheat and other cereals respond very well to bone meal particularly in acidic soils. Sugarcane, vegetables, fruits, leguminous crops, pastures and grasses are all benefited by this manure.
Bone meal is applied to the soil at sowing time or just before it. Its use as top-dressing is not recommended. It is preferably drilled in the soil. A dose of 112-224 kg per hectare is sufficient for most cereal crops. For vegetables and fruits, about 500 to 600 kg of bone meal per hectare is applied.
LIVESTOCK AND HUMAN WASTES
Knowledge of livestock waste characteristics in fundamental to the development of feasible waste management and their efficient utilization. Basic information on the frequency of animal manure excretion, quantity of manure and their characteristics permits specific recovery of waste components, by-product development, fertilizer value and reuse of manure as animal feed and as soil conditioner. The term livestock waste means (i) fresh excrement including both solid and liquid portions, (ii) total excrement, including the bedding material, litter to absorb the liquid component, (iii) the material after liquid run-off, evaporation of water and other volatile components and leaching of soluble nutrients, and (iv) material obtained following aerobic or anaerobic storage of livestock manure.
The feasible approach to characterize livestock waste is to obtain random samples of the solid and liquid waste and analyze for their ingredients. To determine the relationship between animal feed intake and waste characteristics, nutritional trials are conducted and the quantity and quality of the wastes are estimated. The results obtained from nutritional trials are accurate but this is a time-consuming and costly process. The quantity and quality of the wastes are characterized after finding out the digestibility coefficients for the feed components, viz., organic matter, crude fibre, nitrogen free extract, ether extract, crude protein, and after working out the mineral balance in the animals, viz. nitrogen, phosphorus, potassium, calcium and magnesium. Many nutritional trials have been conducted with different livestock like cattle, buffalo, goat, poultry, pig, etc. in national laboratories, veterinary and animal science colleges of agricultural universities in India which can form the basis for assessing the livestock waste characteristics.
The characteristics of livestock wastes are functions of the digestibility, composition of the feed ration and the species of animals and their physiology. The wastes from ruminants such as cattle, buffalo, goat and sheep have a different composition than the wastes obtained from pigs and poultry, which are highly digestible. The faeces of livestock consist chiefly of undigested food, which has escaped bacterial and digestive enzyme action. Faeces also contain residue from digestive fluids, waste mineral matter, worn-out cells from the intestinal linings, mucus, bacteria and foreign matter such as dirt consumed alongwith food. Undigested protein is excreted in the faeces and the excess nitrogen from the digested protein is excreted in the urine as uric acid or urea. Potassium is absorbed during digestion but eventually most of it is excreted through urine. Calcium, magnesium, iron and phosphorus are excreted mostly in the faeces.
A number of methods are used to describe the characteristics of livestock wastes. They can be described on the basis of pollutional nature in terms of B.O.D. (Biological oxygen demand), C.O.D. (Chemical oxygen demand), solids per cent, volatile matter content, nutrient and fertilizer value. The data normally available pertains to the quantity of solid or liquid or combined manure in terms of kg or litre per animal per day. This method of quantification is most realistic in estimating the gross wastes generated at a particular livestock production unit. Besides, other parameters like available nutrient content in terms of fertilizer value, viz. nitrogen, phosphoric acid and potassium oxide can also be determined depending upon the utility of the waste. Livestock wastes are generated as a semi-solid and has to be handled and utilized in this condition. However, liquid or slurry waste system has been considered where the waste can be handled as liquid and transported by pumps and spreaders.
The available information on the quantitative and qualitative nature of livestock excreta should be used to assess and to develop order of magnitude information concerning the potential livestock waste availability. Although it is difficult to apply average livestock waste production values to a specific location, knowledge of average values is very useful for assessing the potential of these wastes and their effective utilization. Hence, the quantity of manure excretion, their characteristics for different livestock from the available literature of metabolism and nutritional trials will be considered.
Bovine Manure, For accurate quantitative assessment of cattle and buffalo dung and urine excretion and their characteristics, the results of nutritional trials conducted at National Dairy Research Institute, Karnal and Indian Veterinary Research Institute, Izatnagar on Sahiwal and Tharparkar cattle and Murrah buffaloes were taken into consideration. The dry matter intake, digestibility, quantity of dung and urine excreted and the nitrogen, phosphorus and potassium balance were obtained to assess the quantitative and qualitative nature of the cattle manure.
The quantity of wet dung and urine excreted by Sahiwal and Tharparkar cattle and Murrah buffaloes is presented in Tables 1 to 3. These Tables provide the information on dry matter intake, dry matter excreted, wet dung and urine produced per day depending on the body weight in respect of different groups of cattle and buffaloes, viz. male calf, heifer, dry and lactating cows and buffaloes. The range of the above parameters depending on body weight, etc. can be seen in Tables 1-3.
The lactating cattle and buffaloes, in general, had the highest dry matter intake as also more excretion of dung and urine. This was followed by dry animals, heifers and male calf. The excretion coefficient of the feed will depend on the nutritive value and digestibility of the dry matter. Even though, the digestibility of the feed consumed by the animal depends on the nature of the feed, it was observed that the Tharparkar breed had the higher excretion coefficient. In the case of Murrah buffalo, the male calves and the non-lactating buffaloes have higher excretion coefficient. The moisture content of the dry dung is a function of type of feed, environmental temperature and humidity. So, the moisture content of the feed, water intake and the season influence the quantity of wet dung and urine excreted.
The composition of the organic fractions in the dung as well as the C:N ratio are presented in Table 4. The dung consisted of about 75 to 85 per cent moisture, 15 to 25 per cent organic matter and 2 to 5 per cent mineral matter. The organic matter of dung mainly comprised of 78 to 90 per cent of total carbohydrates (crude fibre +nitrogen free extract), 9 to 18 per cent of crude protein and 2 to 5 per cent either extract. In the case of Sahiwal cattle, the excretion coefficient of crude fibre varied from 20.8 to 44.8 per cent, whereas that of nitrogen free extract varied from 30.4 to 48.2 per cent. In the case of Murrah buffaloes, the excretion coefficient of crude fibre varied from 20.2 to 37.3 per cent, whereas that of nitrogen free extract varied from 35.3 to 56.8 per cent. In the case of lactating Sahiwal cattle, the excretion coefficient of crude protein was only 17.3 per cent, whereas in Murrah buffalo it was 30.8 per cent. The C:N ratio of the dung for cattle and buffalo varied from 19.57 to 49.83 depending upon the feed material. With berseem feeding the C:N ratio of dung excreted by Sahiwal lactating cattle was 28.85, whereas with lucerne hay feeding the buffalo heifer excreted dung with a C:N ratio of 19.57. With wheat bhusa feeding, the buffalo male calves excreted dung with a C:N ratio of 40.77, whereas with wheat straw and jowar feeding, the dry buffalo excreted dung with a C:N ratio of 49.83. Hence, a higher C: N ratio was observed with feeding of bhusa or straw rather than with green fodder.
The nitrogen and phosphorus balance of Sahiwal and Tharparkar cattle and Murrah buffaloes is presented in Table 5. The excretion of nitrogen through dung varied from 38 to 53 per cent of the total nitrogen excretion. In the lactating cattle, where the nitrogen-outgo through milk was of the order of 18.3 per cent, the N-outgo through dung was 19.7 per cent. In the case of lactating Murah buffalo with 20.3 per cent N-outgo through milk, the N-outgo through dung was 37.4 per cent and 42.3 per cent through urine. The phosphorus excretion through dung varied from 89 to 98 per cent of the total P-excreted. In the case of lactating animals with 23 to 36 per cent P-outgo through milk, the dung P-outgo ranged from 63 to 79 per cent only. The excretion of nitrogen and phosphorus not only depended on their intake by animals but also on the age group of animal, on the season and the metabolic body size of the animal.
The potassium oxide excretion is normally not reported in metabolism trials but the available data pertains to male calves and bullocks only (Table 6). The outgo of K2O through dung varies from 8 to 17 per cent only of the total K2O excretion, whereas the urine contains most of the potash excreted.
Goat and Sheep Excreta. The goat with a body weight of 20 and 40 kg excretes 0.320 to 0.625 kg dung and 0.374 to 0.498 litres urine, whereas the sheep with a body weight of 25-40 and 50-60 kg-excreted 0.370 to 1.430 kg dung and 0.350 to 0.950 litres urine per head per day. The chemical composition of their excreta showed that dung had a dry matter content of 42 to 48 per cent, which constituted 46-51 per cent of the dry matter intake. The organic fraction of the dung comprised 5.2 to 9.3 per cent crude protein, 1.4 to 1.9 percent ether extract, 27.8 to 36.4 per cent crude fibre, 40 to 47 per cent nitrogen free extract and 0.35 to 0.77 percent ash.
The excretion of nitrogen and phosphorus in goat dung and urine is presented in Table 7 and that of nitrogen, phosphorus and potash of sheep excreta is presented in Table 8. It was observed that the dung comprised 30 to 50 per cent total nitrogen excretion, all phosphoric and 90.95 per cent of potassium. In castrated ram, the urination was observed less than once per hour and yielded 150 ml per urination. The total output of urine ranged from 1700 to 2000 ml/day/head. The urine comprised mainly 68.85 per cent of urea-N and 11.16 per cent ammonia-N. The average composition of N, P2O5 and K2O in goat and sheep dung comprised 0.65 per cent, 0.5 per cent and 0.03 per cent and that in urine 1.70 per cent, 0.02 per cent and 0.25 per cent, respectively.
AVAILABLE ORGANIC MATERIALS AND PLANT NUTRIENTS
The Importance of agricultural wastes in general and agro-industrial products in particular has been recognized during the recent years and literature on Indian local organic resources and their possible utilization has been compiled.
Organic Resources and Potential. India has vast potential of manurial resources and major resources are listed below:
A. Livestock and human wastes
Â Â Â Â Â Â Â Â Â (i)Â Â Â Â Â Â Â Â Â Cattle-shed wastes such as cattle and buffalo dung, and urine.
Â Â Â Â Â Â Â Â Â (ii)Â Â Â Â Â Â Â Â Â Other livestock and human excreta.
Â Â Â Â Â Â Â Â Â (iii) Â Â Â Â Â Â Â Â Â Byproducts of slaughterhouses and animal carcasses: Blood and meat wastes, bones, horns and hooves, leather and hair wastes.
B. Crop residues, tree wastes and aquatic weeds
Â Â Â Â Â Â Â Â Â (i) Crop wastes of cereals, pulses and oilseeds (wheat, paddy, bajra, jowar, gram, moong, urad, cowpea, arhar, masoor, groundnut, linseed etc.)
Â Â Â Â Â Â Â Â Â (ii) Stalks of corn, cotton, tobacco, sugar-cane trash, leaves of cotton, jute, tapioca, arecanut, tree leaves, water hyacinth, forest litter, etc.
C. Green manure. Sunnhemp (Crotalaria juncea), dhaincha (Sesbania aculeata), cluster beans (Cyamopsis tetragonoloba), senji (Melilotus parviflora), cowpea, (Vigna catjang), horse-gram (Dilichos biflorus), pillipeasara (Phaseolus trilobus), berseem (Trifolium alexandrinum), etc.
D. Urban and rural wastes
Â Â Â Â Â Â Â Â Â (i)Â Â Â Â Â Â Â Â Â Rural and urban solid wastes.
Â Â Â Â Â Â Â Â Â (ii)Â Â Â Â Â Â Â Â Â Urban liquid wastes - sewage and sullage.
E. Agro-industries byproducts.
Â Â Â Â Â Â Â Â Â (i) Â Â Â Â Â Â Â Â Â Oil-cakes, Â Â Â Â Â Â Â Â
Â Â Â Â Â Â Â Â Â (ii) Â Â Â Â Â Â Â Â Â Paddy husk and bran,
Â Â Â Â Â Â Â Â Â (iii) Â Â Â Â Â Â Â Â Â Bagasse and press mud,Â
Â Â Â Â Â Â Â Â Â (iv) Â Â Â Â Â Â Â Â Â Sawdust,
Â Â Â Â Â Â Â Â Â (v) Â Â Â Â Â Â Â Â Â Fruit and vegetable wastes,Â
Â Â Â Â Â Â Â Â Â (vi) Â Â Â Â Â Â Â Â Â Cotton, wool and silk wastes, and
Â Â Â Â Â Â Â Â Â (vii) Tea and tobacco wastes.
F.Â Â Â Â Â Â Â Â Â Marine wastes. Fishmeal and seaweeds.
G.Â Â Â Â Â Tank silts.
Cattle and Buffalo Dung. The estimate of annual production of bovine dung in India on the basis of Livestock Census, 1966 was estimated to be 344.5 million tonnes and 1335 million tonnes (NCAER, 1965). Garg reported that the bovine urine production was approximately 370 million tonnes per annum. But no systematic survey was conducted to estimate the dung and urine excretion in India. Hence, an attempt has been made to formulate a relationship between the dung excretion and feed intake as well as urine excretion on the basis of feed availability for cattle and buffaloes. They quality of wet dung and urine excreted by 178.865 million cattle and 57.941 million buffaloes was assessed on the basis of the feed availability data reported from the pilot surveys conducted by IARS, Delhi.
The digestibility coefficients of different feeding materials in metabolism trials were worked out for the green and dry fodder and concentrate, taking into consideration their dry matter content. The excretion coefficient was calculated on the basis of 100 per cent digestibility coefficient and the moisture content of the dung has been taken as 80 per cent. The dung excretion formula was calculated by taking the digestibility coefficient of 65 per cent for green fodder, 55 per cent for dry fodder and 70 per cent for concentrate feeding from the available literature on nutritional trials conducted at NDRI, Karnal and IVRI, Izatnagar and other trials.
The total organic matter of the bovine excreta was calculated taking the dry matter content of dung as 20 per cent and the organic matter content as 94 per cent of the dry matter.
The daily feed availability for cattle and buffalo in different states of India was reported (IARS. 1956-67). The average feed availability for Indian cattle was worked out to be 3.311 kg green fodder, 4.134 kg dry fodder and 0.186 kg concentrate. The daily feed availability for buffaloes in India was worked out to be 4.10 kg green fodder, 4.08 kg dry fodder and 0.177 kg concentrate. It was observed that in the northern states like Punjab, Haryana and Union Territories of Delhi and Chandigarh, the adult females are fed with 9.10 to 9.25 kg green fodder for cattle and 11.05 to 13.0 kg for buffaloes. But, moderate green fodder supply to adult female cattle and buffaloes was observed in Rajasthan, Bihar, Assam, Jammu and Kashmir and Uttar Pradesh. In other states, where less green fodder is available, more of dry fodder (bhusa and hay) was given. In the case of Kerala the lowest feeding of both green and dry fodder was observed.
The state wise annual outturn of urine from different groups of cattle and buffaloes in India is given in Table 3. The annual outturn of urine from cattle amounted to 480.148 million tonnes, whereas from buffaloes it amounted to 178.753 million tonnes. Among cattle the percentage distribution of urine by different age groups is as follows: young stock = 16.23, adult female = 30.80 and adult male = 52.97. In the case of buffaloes, the percentage production of urine for different age groups of animal is as follows: young stock = 22.42, adult female = 60.24 and adult male = 17.32. The total annual outturn of urine from cattle and buffaloes in India was 658.90 million tonnes and the overall dung excretion worked out to be about 1.552 times of urine excretion.
If the entire wet dung and urine excreted by the bovines is conserved for manurial purposes, its potentiality for soil nutrients has been worked out as under: 188.380 million tonnes organic matter, 2,822 million tonnes nitrogen, 1.069 million tonnes of phosphoric acid and 1,819 million tonnes of potassium oxide (Table 4). According to Garg the annual production of dung and urine was estimated to be 1300 million tonnes and 370 million tonnes respectively and the potential total soil nutrients had been worked out as 4.89 million tonnes nitrogen, 1.37 million tonnes phosphoric acid and 3.85 million tonnes potassium oxide. According to IARS survey the available bovine dung that could be collected from households was 344.5 million tonnes and its manurial potential had been worked out as 1.206 million tonnes nitrogen, 0.517 million tonnes phosphoric acid and 0.689 million tonnes potash. They reported that nearly 29 per cent of the dung collected in households are burnt as fuel cakes, 69 per cent used for making manure and 2 per cent used for other purposes. However, the present report gives a realistic estimate as to the possible excretion of total dung and urine from the bovines in India.
Other Livestock and Human Excreta. According to Livestock Census 1972, India has a population of 108.419 million sheep and goats, 6.456 million pigs, 136.768 million poultry and 3.301 million other livestock including 0.966 million horses and ponies, 1.126 million camels, and 1.209 million other livestock. The present human population is 625.8 million. The annual excretion of dung and urine by different livestock and human beings is given in Table 4. The annual excretion of bovine dung and urine comprises 82.71 percent of the total excretion by all other livestock and human beings. The sheep and goat excreta comprised 12.228 million tonnes dung and 7.918 million tonnes urine/year. the pig excreta comprised 4.596 and 3.990 million tonnes of dung and urine respectively. The poultry excreta per annum was 3.395 million tonnes. The excreta from other livestock comprised 6.024 and 4.095 million tonnes dung and urine per year respectively. The human excreta comprised 15.16 per cent of the total livestock and human excreta. The human beings excreted annually 30.380 million tonnes faeces and 274.100 million tonnes urine.
The annual manurial potential of bovine excreta alone is 2.822, 1.069 and 1.819 million tonnes N, P2O5 and K2O, respectively (Table 4). The manurial potential of human excreta is 3.228, 0.776 and 0.715 million tonnes, N, P2O5 and K2O, respectively (Table 6). The total annual manurial potential of all livestock and human excreta is 6.414, 1.973 and 2.662 million tonnes, N, P2O5 and K2O, respectively.
Slaughterhouse wastes. There are about 3,000 slaughterhouses in the country handling annually nearly 40 million sheep and goats and 1.5 million buffaloes. About 12 million dead large animals are available annually. No systematic steps are taken towards organized collection of bones from dead animals and their utilization.
Bonemeal. According to the report of the Directorate of Marketing and Inspection, it is estimated that about 4.5 lakh tonnes of bones are available every year in the country, out of which 1.36 lakh tonnes are collected and utilized by bone crushing mills.
Bonemeal is obtained as powder by crushing of bones, and it is used as fertilizer. Steamed bonemeal is obtained by treating the bones with steam under pressure and is used chiefly as phosphatic fertilizer. It also contains about 1 to 2 per cent nitrogen besides P2O5 (25 to 30%). Enormous amount of nitrogen and phosphate can be supplied by proper utilisation of bonemeal potential.
Bonemeal is considered useful for most of the soils and the best results are obtained in acidic soils. It is less effective in heavy clay and calcareous soils. It is more useful in soils well supplied with organic matter. Paddy, wheat and other cereals responded very well to application of bonemeal, particularly in acidic soils it can also be used for sugarcane, vegetables, fruits and legume crops.
Bonemeal is likely to be contaminated with Salmonella, spores of Bacillus anthracis causing an anthrax disease in cattle and other pathogenic organisms. It can be made safe by sterilization.
Blood and Meat-meal. Blood-meal is used as nitrogenous fertilizer or as animal feed. The method for collection is faulty and therefore a large amount of blood is wasted. Availability of blood-meal is estimated about 55,000 tonnes and of this only one-third is utilized. It contains 10-12 per cent N, 1-2 per cent P2O5 and 1 per cent K2O and its C/N ratio ranges between 3 and 4. It decomposes readily in soils. It can be used at any time during growth of crops. Solid slaughter-house wastes consist of waste meat, intestines, offal, etc. and has good manurial value. It is practically a waste at present. It is estimated that 0.12 lakh tonnes of meat-meal can be produced from dead animal wastes. If dried and ground, it will make a good fertilizer containing 8-10 per cent N and 3 per cent phosphoric acid with a C/N ratio between 2 and 3.
Hoof and Horn-meal. This is obtained by grinding hoofs and horns and animals after drying. It contains 10-15 per cent N, 1 per cent P2O5 and 2.5 per cent lime.
Leather Wastes. It is estimated that nearly 5,000 tonnes of leather wastes can be collected from slaughtered and falled animals of total estimated to be 52 million heads for use of organic fertilizer. This remains unutilised at present.
Crop Residues and Aquatic Weeds
Crop Wastes. The potential of crop residues/straw of some of major cereal crops and pulses is given in Table 7. The straw yields have been worked out on the basis of average grain-straw ratio of different crops as indicated in the Table. It is clear from the table that there is huge quantity of renewable crop residues produced every year in the country. The five major crops alone yield approximately 141.2 million tonnes of straw and approximately 10 million tonnes of legumes residues. On average, cereal straw and residues on maturity contain about 0.5 per cent nitrogen, 0.6 per cent P2O5 and 1.5 per cent K2O. The quantity of nutrients in legume residues is much higher than in cereal straw. The nutrient potential of cereal straw/residues is 0.7 million tonnes of nitrogen, 0.84 million tonnes of P2O5 and 2.1 million tonnes of K2O. Even if 50 per cent of these crop residues are utilized as animal feed, the rest should be mobilized for recycling for their plant nutrient potential and other beneficial effect on soils and plants. The role of crop wastes in maintenance of soil organic matter under tropical and sub-tropical conditions needs no emphasis. Crop residues can be recycled either by composting, or by way of mulch or direct incorporation in the soil. Farmers should be advised by the Extension workers to conserve these manurial resources and suggest proper methods for utilization of crop wastes.
Water Hyacinth. Water hyacinth (Eichhornia crassipes) is a free floating weed plant which grows luxuriantly in ponds, lakes and water reservoirs. It is estimated that total areas under this weed is about 292,000 ha in Bengal, Bihar, Assam, Eastern U.P., Andhra Pradesh, Tamil Nadu, Orissa and Kerala. The adverse effects of such uncontrolled growth on agriculture, fisheries, transport and human health are obvious and the necessity for its collection and consequent disposal are needed.
Source of Mulch and Manure. Water hyacinth can be used as soil mulch, green manure and compost. Recently attempts have been made to use water hyacinth for biogas production without loss of plant nutrients. Water hyacinth is used as mulch in tea gardens during dry season for conservation of soil moisture and regulation of temperature. The plants can directly be ploughed in the soil and allowed to decompose for a month or so before sowing of a crop. However, the problem is that as plants are bulky, it is difficult to handle and transport to long distances.
Composting. The fresh plant contains 95.5 per cent moisture, 3.5 per cent organic matter, 1 per cent ash, 0.04 per cent nitrogen, 0.06 per cent phosphorus (P2O5) and 0.2 per cent potash (K2O). This is a good source of potassium. It can be converted into compost without additional source of nitrogen. Addition of small amount of soil will accelerate the process of composting of water hyacinth. Since yields of water hyacinth are of the order of 250 tonnes per hectare per year, there is a potential for producing 3 million tonnes of compost annually in the country which will provide on dry basis about 20.5 kg N, 11.0 kg P2O5 and 25.0 kg K2O per tonne. Water hyacinth compost is good for crops like rice, potato, maize, jute and vegetables. The recommended doses of compost for rice, maize and jute is 20, 5 and 7.5 tonnes per hectare, respectively.
Forest-litter Manure. It is estimated that about 15 million tonnes of compost can be obtained from forest-litter annually without in any way adversely affecting the natural regeneration of the forests. If a portion of the surface litter is removed in a regular manner, the manurial value of forest-litter is as good as farm compost. Fifteen million tonnes of forest litter manure may contain 0.075, 0.03 and 0.075 million tonnes of N, P2O5 and K2O respectively. At present, however, considerable amount of leaf litter is burnt and huge quantities of plant nutrients allowed to go waste.
Green Manuring. Legume plants are grown for fixing atmospheric nitrogen through Rhizobium symbiosis and plants after 8 weeks of growth are incorporated in soil to improve its fertility for raising another crop. Sunnhemp, dhaincha, clusterbeans, senji, cowpea, moong, urid, fodder legumes, etc. are used as green manuring crops. Dhaincha and sunnhemp are more popular. Green manuring is confined to certain areas and in extensive agriculture. This practice has not extended in recent years. There are certain other practical difficulties such as lack of water supply for growth of green manure crops which are ascribed to its non-acceptability by the farmers.
Joffe indicated that the following single crop was only benefited due to green manuring and the favourable effect was not due to its contribution towards the improvement of organic matter and nitrogen content of soil. It was reported that the decomposition of legume residues was much faster as compared to farmyard manure and cereal residues and did not improve organic matter status of soils. Singh also indicated that â€˜legume effectâ€TM was more important as his experiments showed that increase in yields was not due to organic matter or nitrogen additions by green manure.
His experiments also showed that berseem, senji and pea left through their root and stubble 89.4, 53.1 and 20.7 kg nitrogen per hectare. Although the practice of green manuring can not be followed in intensive agriculture on a large scale, but certainly a fodder or grain legume can be included in multiple cropping sequence. Crop rotation involving sugarcane, cotton and arhar (pigeonpea) is ideal. Moreover, growing of legumes can save a certain amount of expensive nitrogenous fertilizers by improving the nitrogen status of soils. However, green manuring practices which do not interfere with the production of main crops should be popularised.
Green-leaf Manuring. Green leaves from trees, viz. Thespesia populnea, Cassia auriculata, Pongamia glabra, Melia azadirachta, Calotropis gigantea, Adhatoda vasica, etc. are collected and used for green manuring in southern parts of India. Weeds, e.g., Croton sparsifolorus, Lucas aspera, Stachytarpheta indica are also utilized for green-leaf manuring.
Some wild legume plants. viz. Gliricidia meculata, Pongamia glabra, Calotropis gigantea, Tephrosia purpurea, Ipomoea carnea, Cassia tora, Sesbania spp., Indigofera teysmann, Tephrosia candida can be grown on bunds and wastelands for utilising their vegetative parts for green-leaf manuring. A programme for raising wild legumes on bunds and wastelands may be developed for increasing its scope for its adoption.
Rural and Urban Wastes
Rural and Urban Solid Wastes. The potential availability of rural and town compost is estimated to be 600 million and 15 million tonnes respectively (Table 8). However, with the present efforts only 310-350 million tonnes of compost is prepared in villages by traditional and improved methods of composting. The present level of production of town compost is only of order of 6.5 million tonnes. However, with the set up of mechanized plants, the potential estimate of city waste is of the order of 50 million tonnes per year.
Sewage and Sullage. At present about 36 million urban population is served by drainage system producing about 292,000 million gallons sewage per annum. Out of this potential, about 91,250 million gallons are utilized on organized sewage farms. It is estimated that during 1978-79 about 4,000 ha of land would be under sewage irrigation. Sewage has important components - water, plant nutrients and organic matter which are badly required in Indian agriculture. There is a scope for further expansion of sewage farming programmes now, and in future more cities will be provided with drainage systems.
Besides the necessity of sewage farming from point of view of utilization of the resources, it is also an effective method to avoid pollution. Unrestricted discharge of city liquid wastes in rivers and streams and on land results in pollution of environment and is a public health hazard.
There are two hundred and twenty sewage farms located in different parts of the country, about 102 such farms are located in six states, viz. Punjab, Uttar Pradesh, Tamil Nadu, Haryana, Gujarat, and Madhya Pradesh. The present utilization of wastewaters is only about 31 per cent of the total potential. The average NPK content of Indian city sewage is 50 ppm N, 15 ppm P2O5 and 30 ppm K2O. Sewage sludge could form an important component of composting.
Waste stabilization ponds have been recognized as effective and economical units for treatment of domestic sewage as well as industrial wastes. It is essentially a microbiological process involving simultaneous activity of bacteria and algae in presence of light, atmospheric oxygen and nutrients in wastewaters. Effluents from stabilization ponds contain algal cells and other nutrients. In addition to oxygenation due to photosynthetic activity, cellular algae are a good source of feed for the growth of edible variety of fish. The effluents from such treatment contain appreciable quantities of organic substances, nitrogen, phosphorus, potassium, etc. In oxidation ponds a part of these nutrients is removed from solution and concentrated in algal cells. The treated sewage effluent is safe and will not cause environmental pollution. The raw sewage contains 60-70 ppm N, 20-25 ppm total P2O5 and 40-45 ppm total K2O and the secondary treated sewage contains 15-20 ppm N, 15-20 ppm total P2O5 and 35-40 ppm total K2O.
Substantial volume of treated or partly treated sewage is usually being led into natural water streams. Thus the nutrients in waste water are not being effectively utilised. The total nutrients from urban and rural communities is substantial which should be recycled.
ORGANIC FARMING IN RICE
Rice is the principal source of nourishment, providing about two thirds of the calories for more than two billion people in Asia and one third of the calorie intake of nearly one billion people of Africa and Latin America. Rice is also the major source of proteins to the masses of Asia and because of the quantity consumed; it is the principal source of energy, iron, calcium, thiamine, riboflavin and niacin in Asian diets. Traditionally rice has been the staple food and main source of income for millions of people and it will continue to be the main stay of life for future generations.
Over the centuries the rice farmers have evolved a culture, which is in tune with the different ecosystems. They have evolved varieties and systems of rice culture to suit every conceivable agronomic condition from totally dry to floating rice; under rain fed as well as irrigated conditions; in sandy to clayey soils and in saline to acidic soils. With the introduction of high yielding varieties, the traditional rice varieties evolved by natural selection and adapted to the different ecological situations were replaced. Modern agriculture, no doubt, has paved the way to â€˜Green Revolution.â€TM But it has led to the application of heavy doses of chemical fertilizers and pesticides with the sole objective of maximizing the yield, totally disregarding the health of soil and balance of ecosystem. The fertilizer consumption of the country has steeply increased from 0.29 million tones in 1960-61 to 17 million tones in 1998-99 (FAI, 2000). Use of herbicides for weed control has increased from 15 tones in 1970 to 7620 tones in 1995-96. The consumption of pesticides in India has increased from 154 metric tones in 1953-54 to 54135 metric tones in 1999-2000.
â€˜Green Revolutionâ€TM has come to be associated not only with higher production through enhanced productivity, but also with several negative ecological and social consequences. Excessive use of chemical fertilizers and pesticides has caused damage to the soil and environment. Fertilizer fed soil cannot support microbial life resulting in less humus and fewer available nutrients in the soil. Indiscriminate use of chemical pesticides causes health hazards by accumulation of toxic chemicals in animals and human beings. Besides, the pesticides and fertilizers persist in the soil destroying the beneficial soil organisms and earthworms and thereby degrading soil fertility. Pesticide residue is the second largest agent causing cancer next to cigarettes. A study in US revealed that risk of cancer due to pesticide is three out of 1000 people.
Maintaining the sustainability and increasing the productivity of agricultural system is of primary importance to feed the present population. The total demand for rice by 2000 is estimated to be around 104 million tones including the indirect demand for seeds. The important questions to be addressed are national food security, nutritional security, maintenance of soil health, enhancement of soil productivity and leaving a good heritage for the future generation. Also there is a felt need to preserve nature and not rob the future generations off their legitimate right over biodiversity. The growth in agricultural production has to be consistent. This becomes possible only if the soil is in good health.
Integration of fish along with rice will help to maintain sustainability. Utilisation of rice fields for integrated farming is a recent development in Kerala. Studies conducted by Kerala Agricultural University at the regional agricultural research station, Kumarakom indicated that in addition to the rice production averaging 3 tones per hectare fish yield ranging from 600-1000 kg per hectare could be obtained by simultaneous farming of rice and fish. Rice fish integration is effective for the management of weeds, pests and diseases and to improve soil fertility.
The primary factor having influence on soil health is the organic matter content of the soil, which is under constant threat of depletion due to environment factors and inadequate replenishment. With the increasing need to conserve natural resources and energy, recycling of organic wastes assumes major importance. Further, in the wake of serious pollution problems and bio-magnification of toxic chemicals in the various biological systems,Â â€˜Organic Farmingâ€TM is the right approach in the present day agriculture.
â€˜Organic cultivationâ€TM practiced in India from time immemorial, but largely given up in recent decades for agro chemicals deserves close attention of the scientific community. Most of the developed countries are now â€˜rediscoveringâ€TM the virtues of chemical free, pro-nature kind of cultivation, through techniques that are friendly to the environment. Organic farming is a holistic system ensuring sustainability in crop production. It is a method of farming system, which primarily aims at cultivating the land and raising crops in such a way as to keep the soil alive and in good health. Although the expanding organic movement is a positive development, in the final analysis, agricultural production will be maintained only if farms are designed in the image of natural ecosystems, combining the knowledge of science with the traditional wisdom. Organic farming aims at restoration of soil fertility and enhancement of the soil microbial activity by the use of organic manures, non-chemical weed management and by biological pest and disease management.
Objectives of Organic Farming
1. Production of poison free food by avoiding pesticides, fungicides and synthetic fertilizers.
2. Maintenance of soil fertility and soil organic matter by use of organic manures & residue management.
3. Recycling of nutrients and minimizing the use of external inputs.
4. Sustainability soil health, by proper crop rotation by using bio-fertilizers, bio-control agents & botanicals.
It is interesting to note that organic farming is nothing new to this country and it is this farming which was practice in India for centuries together before the introduction of high yielding varieties and synthetic fertilizers. Some of the traditional practices were as follows.
1. Use of traditional & tolerant rice varieties & rotation with legume.
2. Digging/tillage to incorporate weeds
3. Digging/ploughing before summer
4. Organic manuring
5. Mechanical methods of pest control
Aspects of Modern Agriculture
With the advent of modern agriculture there were
1. Genetic improvement of crops through breeding (conventional & molecular)
2. Production and use of fertilizers, insecticides, fungicides and herbicides
3. Farm mechanization
4. Post-harvest processing & value addition
The modern agriculture though was essential to meet the food grain targets of ever growing population of this country, resulted in the indiscriminate use of fertilizers and plant protection chemicals. The present hype for organic farming is mainly due to the following factors.
-The consumers increasing awareness of environmental and health issues.
-Introduction of legal guidelines for production, commercialization and export of organic products.
-Increasing availability of high-quality organic products
-Increasing involvement of supermarkets in the sales of organically grown food.
Important Regulations for Organic Farming
1. Organic manures, soil conditioners and fertilizers of natural origin permitted (Plant and animal origin) FYM, Slurry, urine, vermi-compost, blood meal, meat meal, bone meal, hoof and horn meal, feather meal, fish and fish products, wool, fur, hair, dairy products.
2. Soil conditioners and natural fertilizers, basic slag, lime, limestone, gypsum, calcareous and magnesium soil amendments, magnesium rock, kieserite, Epsom salt, naturally occurring potassium minerals, natural phosphates, trace elements, sulphur.
3. Micro biological materials, biodegradable processing byâ€"products of microbial origin, biofertilisers.
Materials Not Permitted
-Synthetic herbicides, fungicides, insecticides, growth regulators
-Genetically engineered organism or products.
The nutrient requirement of rice is quite high (5 t OM & NPK @ of 90:45:45 or 70:35:35 kg/Ha). Hence, one of the most difficult tasks in organic farming in rice is to meet the entire requirement through organic means alone. Some of the options for the same are given below.
Green Manure: Green manuring is of two typesâ€"Green leaf manuring which is practice of growing leafy crops on the bunds or nearby waste lands, harvesting the leaves & tender twigs and incorporating the same into the filed at the time of land preparation. In site green manuring refers to growing a green manure crop in same filed during the off-season and incorporating the same at the time of land preparation. The amount of N contributed depends upon the species and vigor of the green manure, and ultimately on the duration of its growth cycle. Typically, a green manure crop will require approximately 50 to 60 days of growth to fix between 20 and 40 kg N per ha. Recent research suggests that the available N from a green manure increases over a four to six-week period following incorporation, and then returns to pre-incorporation levels. Therefore, crops following a green manure rotation may require additional applications of N later in the season. The green manure crops may also harvest N, P and K from deep in the soil profile and make them more available to the succeeding crop.
Compost: Compost is a relatively cost-effective commercial organic source of N. Compost also provides P, K, Ca, Mg, S, and other minor nutrients in fairly well balanced amounts. Although actual concentrations of P and K in compost are low, the total additions may be quite high due to the high volume of material applied. When applying compost, the challenges are to know and understand its composition and to determine how to use it most efficiently. The grower should understand the composting process used by the supplier and know the sources of raw material used. If the materials that are being composted are low in nutrients, the compost will have a low nutrient analysis. Poor-quality or immature compost may actually tie up nitrogen in the soil and decrease the availability of N to the growing crop. The carbon-to-nitrogen ratio (C:N) of compost is one indication of the maturity and N availability. As the C:N ratio rises above 20:1, the tendency for N from the soil to get immobilized increases. A compost with a C: N ratio of less than 20:1 will generally release N to the succeeding crop.
Three types of composts are available to organic farmers viz., normal compost (NADEP), vermine-compost and biodynamic compost. The composition of these composts varies and should be considered before deciding the rate of application. Use of suitable microbial cultures may accelerate the process of composting and addition of Azotobacter can increase N content of the compost. Similarly, Addition of natural P sources such as rock phosphate can enrich the compost.
Animal Manure: Decomposed animal manure (FYM) can also be a balanced source of N and other major and minor nutrients. Fresh manure may be of limited use because of relatively high transport costs and the potential for pollution problems. Another potential limitation with manure is the availability of a consistent supply of a material that is uniform enough to be confidently incorporated into a production programme. Organic certifying agencies may limit the type or timing of applications of manure on organic production fields. A public perception of increased food-safety-related problems relating to manure fertilization might further limit the use of manure.
Other Commercial Organic Fertilizers: A number of approved organic fertilizers or natural materials are available commercially. Many of these materials are by-products of fish, meat and soybean processing industries. The commercial formulations and nutrient analysis of these materials vary considerably. In general, they range from 1 to 12 percent N and provide P, K or both along with N. Other simple fertilizer materials that offer only one macronutrient include:
Blood meal (N)
Rock phosphate (P)
Potassium sulfate (mined) (K)
Certain by-products of the meat processing industry, such as blood and bone meal, have recently come under scrutiny because of food safety concerns and the potential for disease transmission.
Minor Element Sources: Organic fertilizer sources commonly contain one or more minor elements. Additional synthetic fertilizers may be permitted by a certifying agency in specific circumstances for correction of minor element deficiencies such as zinc or copper deficiency. Application of approved source materials will raise soil levels to a range where they are not deficient.
Special-Purpose Fertilizers: Specific approved nutrients sources of K, Ca and Mg may be useful to an organic grower when a deficiency or imbalance is indicated by a soil test. Materials such as gypsum, lime, and potassium-magnesium sulfate have been in use in agriculture for many years and their value is thoroughly tested. These materials may be used to correct deficiencies or imbalances of potassium, calcium, or magnesium, and lime may be used to raise soil pH. Gypsum also is often applied to replace exchangeable sodium prior to leaching a high-sodium soil (user land) or to improve water infiltration on clay soils with poor structure. Pyrites may also be used as amendment for sodic soils.
Biofertilizers : Three types of biofertilizers are used viz., (i) Symbiotic N2 fixers such as Rhizobium culture for legumes, (ii) freeÂ living N2 fixers (non-symbiotic bacteria) such as Azotobacter and Azospirillum sp. for cereals, blue green algae and Azolla for rice and (iii) P solubilizers such as Pseudomonas sp. While symbiotic N2 fixers inoculated in legumes can fix substantial amount of atmospheric N2 to feed the host plant, free-living N2 fixers contribute much less, usually 10-30 kg/ha. P solubilizers enhance the availability of native inorganic P.
Ecofriendly Management of Pests and Diseases in Rice
1. Host Plant Resistance
Host plant resistance is the most effective, economical, practical and easiest means of encountering the pest problems and it is compatible with all other methods of pest control. Most of the modern varieties released and grown widely in pest prone areas possess resistance to at least one insect pest or disease. In Kerala most of the recently released rice varieties are resistant to pests & diseases. Many of these resistant varieties possess high yield and other desirable agronomic characters and are being extensively cultivated in the pest prone areas as a principal method of control or as a supplement to other methods of insect pest management.
2. Cultural Control
Cultural practices are normal agronomic practices that are followed for increasing crop productivity and at the same time useful in pest suppression. Strategic manipulation of these practices can effectively suppress the multiplication or spread of insect pests. These include:
a) Early and Synchronous Planting: Wherever possible, altering the date of planting can often check the development of populations of insect pests like yellow stem borer, gall midge, BPH, WBPH and GLH. However, this needs community action and often depends on availability of water in command areas in irrigated rice situations.
b) Cropping Pattern or Crop Rotation: These are important to break continuity in insect pest buildup or in disease cycle, which has been successfully attempted in Rice Tungro disease endemic areas.
c) Field Sanitation: Stubble destruction soon after havesting effectively prevents carry over of stem borer and gall midge. d) Other practices : Provision of alleyways of 30 cm width after every 2-3 meters is useful, particularly in BPH/WBPH endemic areas.
d) Water Management: Simple practices like draining of water from the fields when abundant plant hopper population or maintaining appropriate levels of water in case of pests like army worm and case worm, etc., can be effective.
3. Use of Botanical Pesticides
Utilization of botanical pesticides, mainly neem formulations is a novel approach as these are safe to humans and environment. Unlike traditional insecticides, neem formulations do not out rightly kill the insect pests but incapacitate them through repellency, growth retardant effect, feeding deterrence, reproductive inhibition and oviposition deterrence. However, in rice ecosystems, neem formulations are only moderately effective against BPH, WBPH, GLH and leaf folder and also slow in action compared to insecticides, which is disadvantageous to farmers in emergency situations.
4. Biological Control
Use of biological agents to manage crop pests is a key component of IPM. The successful use of several entomophagus and entomopathogens in the control of pests has projected biological control as a promising alternative to ecologically disruptive chemical control measures. In India, unlike in other crops, the scope of using biocontrol agents through inundative or inoculative releases in rice is restricted to the egg parasitoid, Trichogramma japonicum against yellow stem borer and T. Chilonis against leaf folder. Five to six release of the egg parasitoid @ 1,00,000 adult parasites/ha in a crop season is very useful and devoid of any side effects. Inundate release of Trichogramma spp. to control stem borers and leaf folders in rice fields is being done across the country by the Central IPM centers of the Directorate of Plant Protection Quarantine and Storage, Government of India, Establishment of mass multiplication units by the State Agricultural Universities in different states has provided the impetus to the use of biocontrol agents in rice.
Conservation of Native Natural Enemies to enhance in situ Biological Control in Rice
Studies have indicated that native natural enemies can be used profitably in pest management. So, increased attention is now being given for the conservation of natural enemies. Several natural enemies identified from different rice ecosystems of the country have been documented. In case of yellow stem borer, the egg parasitism due to Tetrastichus, Telenomus and Trichogramma is very high in nature and needs to be conserved, while in case of gall midge, the parasitism due to Platygaster oryzae has little impact on the pest in the field. The larval and pupal parasitism of leaf folder under natural conditions is also high and effective. In case of leaf and planthoppers, the action of predatory spiders like Pardosa, Tetragnatha, Argiope, Araenus, Oxyopes, etc., and mirid bug, Cyrtorhinus lividipennis have been observed to be more common and dominant. The other general predators like dragonflies, damselflies, ground beetles, staphylinids, and earwigs have also been found effective in keeping the pest populations at lower levels.
Use of Bio-Pesticides
Use of microbial pesticides like Bt (Bacillus thuringiensis) formulations with endotoxins is another useful approach. They are specific to insect pests and quite safe to humans, natural enemies of insect pests and other non-target organisms. Evaluation of some of these formulations has revealed that they are effective against leaf folder and moderately effective against stem borer. Some of the fungal pathogens such as Beauveria bassiana against rice hispa and Pandora delphacis against BPH etc. have also been found promising. There is a need for a suitable mechanism to develop suitable formulation technology; proper marketing and commercialization of these products for possible use in rice IPM in future.
PRODUCTION OF ORGANIC COMPOST
Production of compost is the heart of the organic method. Dying and decaying matter, whether the falling leaves of the forest or the decaying bodies of more complex life forms, is constantly being used as the raw material of new life. In nature, the forest floor is the workshop for a continuous compost production operation. In agriculture fields, this normal cycle is interrupted by taking out some of the organic material produced. In setting up a compost-making operation, we are restoring the cycle and returning to the soil the humus, which is the single most important element in its fertility. The process of compost or life renewal is achieved by a remarkably complex interaction of billions of microscopic life forms with biological materials.
Composting is a biological decomposition process that converts organic matter to a stable, humus-like product under controlled conditions. During the composting process, microorganisms utilize the decomposable microbial substrates present in the organic compost both as an energy source and for conversion to microbial substances.
The composting process is simply a means of converting raw organic compost, a potential source of odor and public health problems, into a safe product called humus. By definition, composting is an alternative system for solving some of the compost handling problems existing on todayâ€TMs farms.
Compost is the dark brown crumbly material that is produced when a collection of plant and animal material is decomposed into fine organic matter and humus. Once the compost has been mixed into the soil it will undergo the process of mineralisation in which the humus releases minerals into the soil, making them available to the plants.
It is natural process, which occurs in nature in which organic matter is decomposed by microorganisms forming a humus-like substance. The process itself is not new. It has been in practice for many centuries by farmers who have stacked animal manure into piles or gardeners who have placed garbage, leaves, grass cuttings, etc., into pits.
Despite its wide usage, no advances were made in the treatment process until 1925 when Sir Albert Howard, a British agronomist stationed in India, developed a systemized process for composting. The improved process was labeled the Indore Method after the stage in central India where it was conceived and tested. The method described by Howard involves the formation of a layered pile about 1.5m high using garbage, animal composts, sewage sludge, straw, and leaves. Initially the process was anaerobic and required 6 months for completion to occur. The process was later modified by turning the pile over twice, which reduced the composting time to 3 months.
During the next 30 years, various method for mechanically composting large quantities of refuse were tested and patented in Europe. Research on composting did not begin in the United States until the 1950s when the University of California at Berkeley embarked on an extensive investigation. These studies were the first to scientifically describe the principles of composting and led to the development of a rational technology. In 1966, the United States Public Health Service supported a demonstration grant in cooperation with the Tennessee, Valley Authority and the municipality of Johnson City, Tennessee, to study the feasibility of composting solid composts and sewage sludge. Since then a great deal of research has been conducted by many of the Land-Grant Schools to determine the feasibility of composting and its value as a means for treating agricultural composts.
IMPORTANCE OF COMPOSTING
A great deal of organic compost from the kitchen and farm can be recycled and given back to the soil in the form of compost. When compost is added to the soil the level of organic matter increased, which is beneficial in many ways:
1. The finished product obtained from composting may have some fertilizer value but it should be strongly emphasized that compose is an excellent soil conditioning agent.
2. Incorporating compost into the soil increases the organic content and improves the texture, the permeability, and the water-holding capacity of that soil.
3. An improvement in humus content, hygroscopic moisture, water retention capacity, and absorption capacity when organic matter is added to the soil.
4. Compost can be used for improving the fertility of marginal and arable land and also for restoration of land that has been severely eroded or strip-mined.
5. Compost can also be used as mulch for nurserymen and vegetable farmers. Compost used as a mulch has advantages over peat moss of bark in that the compost releases absorbed water more readily than does peat moss, and imposes a lesser demand on soil nitrogen than does bark.
6. Compost is an excellent material for litter or bedding. It is moisture absorbent, odorless, and eliminates the need to purchase bedding from an outside source.
Maximizing the Nutrients Availability from Agricultural Compost
Digested agricultural compost should be applied at rates to supply adequate nutrients for crop needs. Rates of application greatly in excess of crop needs are undesirable since that means nutrients are not being used effectively and the risk of soil and water pollution is increased. In the past, when manures were valued for their plant nutrients, the normal rate of application was between 25 and 50 tonnes/ha/annum or 5 to 10 tonnes of manure dry matter. Now manures are often applied in much higher quantities of disposal rates of up to ten times the traditional rates. However, such rates could not be recommended either from an agricultural or environmental viewpoint. Approximately 100 tonnes of 4% dry matter slurry would be required to supply the same quantity of nutrients as 50 tonnes 8% dry matter slurry.
It is clear that the potassium level at this rate is over double the maintenance requirement of most agricultural crops, while the nitrogen and phosphorus rates are high but not excessive. In fact, if only 50% of the nitrogen is available, supplementary fertilizer would be ncessary for maximum yield of many crops. If 100 tonnes/ha of pig slurry were used, then 300 kg N, 90 kg P, and 150 kg K would be applied. In this case, the phosphorus level is in excess of the needs of most agricultural crops but the nitrogen and potassium levels are not excessive. The 100 tonnes of cattle slurry would supply 8 tonnes dry matter and the pig slurry would supply 4 tonnes dry matter per hectare based on dry matter.
Note: C:N values should be regarded only as approximations and will vary according to age precise make-up, etc. They are best used for comparative purposes to balance high C:N and low C:N materials at opposite ends of the table. A wide range of ingredients is the safest bet and will ensure a nutrientrich compost, especially if seaweed and comfrey are added, even in small amounts. Wood ash, supplying potash and lime, may also be used. Lime need not normally be added to the compost pile, unless you have an acid soil. Care should be taken with pet manure: cat and dog faeces can sometimes be hazardous if handled.
From the above values, it is evident that the amounts of nitrogen, phosphorus, and potassium in manure are not in the correct proportion for many crops. There is generally too much potassium in cattle slurry and too much phosphorus in pig slurry relative to the other nutrients. To maximize the value of nutrients in manure, cattle slurry should be applied at rates to give adequate potassium for crop need and he supplemented with fertilizer nitrogen and phosphorus. Pig slurry, on the other hand, should be applied at a rate to supply adequate phosphorus and be supplemented with fertilizer nitrogen and potassium. The same approach can be used to estimate the application rate of other composts so as to maximize the fertilizer benefit of the nutrients present.
Where more composts are available than are required for the crop nutrient needs, most crops will tolerate higher application rates. For example, cattle slurry could be applied at a rate to supply adequate phosphorus for the crop, and the maximum yield when relying on nitrogen from cattle slurry alone, as high rates of application may depress yield.
A dressing of 40 to 50 tonnes/ha of good slurry is suitable for most root crops. As for silage, cattle slurry normally needs to be supplemented with phosphorus and pig slurry with potassium fertilizer. Nitrogen fertilizer may also be necessary, and the rate will depend on crop requirements. Care is needed when using compost for cereals because of their sensitivity to excess nitrogen and the difficulty of applying accurate rates of nitrogen due to the variation in compost composition.
Effect on Soil and Crop
Composts can have considerable effects on the composition of soils and crops. Soil analyses on experimental plots indicated that land receiving cattle slurry had high soil potassium levels and land receiving pig slurry had high levels of phosphorus. The manganese content of grass from cattle slurry treated plots was significantly lower than with fertilizer treatment. Copper sulphate is added to the diet of fattening pigs and the slurry may contain several hundred parts per million on a dry matter basis. Crops receiving pig slurry can contain increased levels of copper. There can also be a higher total removal of phosphorus from pig slurry than from fertilizer or cattle manure treatments. The higher phorphorus removal is probably due to the higher soil phosphorus level on pig slurry treatments.
In addition, the slurry provides a micro-environment that can facilitate seedling growth in otherwise inhospitable conditions.It is important to ensure that the ammonia content of the slurry is not so high that it can inhibit seed germination. Composts can also be used to provide a micro-environment for seedling development in reclamation of land; it can be particularly valuable in the rehabilitation of mine heaps and other industrially disturbed soils. In these situations, the composts are often superior to inorganic fertilizers as they have the dual benefits of improving the physical environment of the plant root and also supplying essential nutrients.
Method of Spreading Compost
Composts cannot be spread at some stages of crop growth; it is usually not possible to spread composts on manure crops near harvesting time. It is also true that some crops are more suitable for compost application than are others. From a fertilizer point of view, spring application in USA and Europe and kharif (rainy season) application in India usually gives best results, supplying maximum benefit from the nitrogen in the compost. However, it is not always possible to spread all compost in the above sections. In pig production, for example, the manure is produced throughout the year, so adequate storage for twelve months would be necessary if all the manure was spread in spring. This would be very costly. In practice, it is customary that manure produced during winter is spread during spring and summer, and that produced in autumn be spread during late autumn. In some situations, where soil conditions are suitable, manure is sometimes spread throughout the year so that very little storage is required.
The pattern of agriculture determines when and where composts can be spread. Traditionally, most compost was spread on tilled land. With intensive agriculture, in areas like the British Isles-compost is spread on grassland. In countries such as Denmark, where most of the land is tilled, a high proportion of the compost is spread for tillage crops. In India, agricultural compost is incorporated in soil for crops.
Time of application of compost is often determined by when soil conditions are dry enough to carry manure spreading equipment. Under some soil and climatic conditions, there may be six months of the year when manure spreading equipment could cause serious damage to the soil surface. Under other conditions, it is possible to spread manure throughout the year without serious soil damage to grass than the same quantity applied in spring or summer. It appears that slurry can deplete the already low oxygen levels in the soil near the grass roots, killing the better yielding grasses, which will be replaced by weeds. It is therefore advisable that if slurry has to be spread on grassland in winter, low rates (say not more than 20 tonnes/ha) should be used.
Rate of Application
The quantities of plant nutrients required for different crop and soil conditions are reasonably well established for most countries, where soil fertility is adequate, maintenance dressings of phosphorus and potassium are applied annually. Maintenance dressings are rates that will maintain soil fertility over the years and should equal the difference between losses and the nutrient supplying power of the soil. The main nutrient losses are crop removal and loss in drainage water. Nitrogen is more complex because there are many sources of losses and inputs and it is the primary nutrient influencing yield in conditions of high soil fertility. With low soil fertility, extra rates of nutrients, above maintenance dressings, may have to be applied initially for maximum crop yield. Losses of phosphorus and potassium in water from agricultural land are small in comparison with crop and potassium in water from agricultural land are small in comparison with crop uptake and are usually in the region of a few kilograms per hectare per annum. Removal by the crop is related to crop yield and composition. Most agricultural soils can supply large quantities of potassium annually from soil minerals. Rates of nitrogen fertilization for agricultural land are normally less than 300 kg N/ha/annum.
Mineralization of plant nutrients and their availability to plants is one of the major consequences of organic recycling in soil. The quantity released depends mainly on the content of a particular nutrient in organic residues undergoing decomposition. In general, there is immobilisation of nitrogen due to decomposition of cereal straw. However, with FYM/compost application no such effect is observed. Addition of FYM and cereal residues results in improvement of total soil nitrogen. The effect of organic matter in reducing the intensity of phosphate fixation by the soil sesquioxides and maintenance of soil fertility by use of organic manures alongwith superphosphate has also been established. FYM remains intermediate in building up available P status of soil. In sub-humid lateritic soils, P use efficiency under rice-rice sequence was increased tremendously with FYM application. Response of crops to organic manuring depends on degree of decomposition of organic residues, C: N ratio, time of application, soil characteristics etc.
Continuous application of organic manures improves the availability of Zn in soil and may not be sufficient to meet the requirements of the immediate crops. Contrary to macronutrients, the range between deficiency and toxicity limits of micronutrients is quite narrow for most of the crops. Inclusion of micronutrients in fertilisation schedule should, therefore be advocated after careful appraisal through soil and plant tests.
Time of Application
To get a good response from compost application, good management practices should be followed. No more than 50 tonnes/ha should be applied in any one application, and there should be at least 30 days between application. Lower application rates would be advised for wet soil conditions or when applying in the wintertime on grassland. Heavy rates of composts, particularly slurry, can block soil pores. This can lead to anaerobic conditions and reduced infiltration capacity, leading in turn, to increased surface runoff during rainfall. The blocked soil pores will usually be cleared within 30 days by microbial flora after breaking down the organic matter. However, if compost is applied at too frequent intervals, soil microoganisms will not be able to clear the blocked soil pores.
Cattle or pig slurry at rates of 45 tonnes/ha applied six weeks before cutting did not reduce silage quality or animal performance (Tunney, 1976a). In order to reduce surface contamination and disease risks, it is advisable that composts should be applied at least four weeks before pasture is grazed.
Classification of Composting
It is classified into following general categories:
Composting, categorized by the amount of oxygen available, is either aerobic or anaerobic in nature.
The composting of municipal refuse and large-scale agricultural composts should be carried out under aerobic conditions. Aerobic composting is governed by the activity of aerobic microbes and hence required the availability of atmospheric oxygen during the period of decomposition. If the environmental factors are optimal, aerobic composting is characterized by high temperature, the absence of foul odors, and a short stabilization period. The high temperatures have a sterilizing effect by destroying weed seeds and pathogenic organisms. Hence, no malodors and its ability to destroy seeds and pathogens.
The Aerobic Heap: A heap should contain enough bulk of food for the heat-loving bacteria for their growth and activity. If the pile is too small, there will be insufficient heat build-up. To obtain a suitable C:N mix on a garden scale, the materials may first need to be assembled over a period of time. This can best be achieved by creating a preliminary stockpile. Garden debris, mowings, weeds and so forth can be loosely stocked and covered in one pile or placed in plastic bags; likewise kitchen compost.
It is governed by anaerobic bacteria that operate in the absence of atmospheric oxygen. The process is characterized by lower temperatures, the production of odorous gases, and longer stabilization times. Since anaerobic composting does not require atmospheric oxygen, the pile or bed can be sealed to prevent the escape of foul smelling gases and left alone. The major advantage of anaerobic composting is that the process can be carried on with a minimum of attention and as such requires little or no energy once the compost bed is established.
The composting process can also be categorized by the operating temperature that exists within the pile. Temperature between ambient and 40oC support mesophilic organisms while temperatures between 40oC and 60oC support thermophilic organisms.
The mesophilic bacteria are more efficient than thermophilic bacteria and, therefore, decomposition occurs more rapidly in the mesophilic region. Those favoring thermophilic composting claim that decomposition proceeds more rapidly at the higher temperatures and in addition pathogens and weed seeds are destroyed.
The temperature in both aerobic and anaerobic composting gradually rises to well within the thermophilic range due to the excess heat energy generated by microbial activity. For this purpose it is essential to understand the effects of temperature and its relationship to microbial activity.
Sufficient air is required to sustain the temperature build-up. Non-special air channels are required. Simply ensure that the material does not get compacted by forking through it and that grass mowings or the like, which are prone to settle into a solid, airless mass, are mixed with woody materials. Temperature is related to the weather, therefore composting is more reliable and fast in summertime. Compost, which may be ready in two summer months, may require six months in winter.
Method of Operation
The composting processes are operated as either enclosed digesters or windrows.
They are mechanized composters that provide aeration by some type of continued tumbling or stirring action. Some methods combine stirring with forced aeration. Such require a high capital investment and utilize a great deal of energy. Composting times for enclosed digesters are 10 to 15 days.
It is characterized by placing the organic composts in elongated piles called windrows. Depending upon the climatic conditions, the windrows may be placed in the open or covered to provide some protection against the elements. Aeration is provided by stirring and mixing the composter with a front-end loader or a specially designed rototiller type of implement. If the windrows are adequately mixed, the process will be aerobic and the composting time required is about 6 weeks. By way of contrast, anaerobic windrow composting takes 4 to 6 months.
Kinetics of Composting
The aerobic composting of all the municipal refuse plants are operated on aerobic process.
The biochemistry or the rate at which organic matter decomposes is affected by the carbon-nitrogen relationship of the organic matter, moisture content, temperature, availability of oxygen, and the pH. The effects of these environmental factors on the decomposition of organic matter will help one to better understand the composting process.
Carbon to nitrogen ratio controls the rate at which composting proceeds. As composting begins, the microorganisms require carbon as a source of energy for growth and nitrogen for protein synthesis. A C/N ratio above this range results in aÂ slowdown of the composting process. If the carbon is present in a form highly resistant to bacterial attack, the C/N ratio can exceed the optimum level indicated. Examples of material that have a large percentage of carbon in a resistant form are paper, fiber, wood, and straw. The C/N ratio and hence the time required for composting can be lowered by adding a nitrogen source such as manure or activated sludge.
A low C/N ratio results in the loss of nitrogen as ammonia. The loss of nitrogen is not detrimental to the composting process; one should attempt to conserve the nitrogen as a soil nutrient.
Ideal C: N Ratio in Heap
The art of making successful compost is largely associated with achieving a correct C:N balance. 30 parts carbon to 1 part nitrogen,/ is ideal which reduces to 10-15:1 when turned into mature content. Fine grass mowings on their own will produce a treacly mass result, so straw, leaves or, possibly, cardboard would be good companions. If you include too much woody material such as bark and prunings without balancing this with sufficient green matter, the pile may not heat up at all.
A compost heap, in fact, is somewhere between a bonfire and natureâ€TMs own method of decomposition, which is a slow rotting process culminating in incorporation by worms into the soil when breakdown is completed. By speeding up the decomposition process one can increase a soilâ€TMs fertility very quickly, especially by making a well aerated heap where oxygen-loving organisms can flourish.
As composting proceeds, the C/N ratio continuously decreases with time, since the nitrogen remains relatively constant and the carbon is released as carbon dioxide gas. The compost is considered ripened once the C/N is lowered to a value between 12 and 20.
Moisture is essential for microbial activity. In a dry summer the heap will definitely need some, preferably, added every so often while you are constructing it. Ingredients should be pretty damp. Too much moisture is unlikely at the time of making the heap, but it should be protected from rain with polythene on top.
The biochemical reactions during composting are ate also influenced by the moisture content of the organic matter. The optimum moisture content should be 100%, but this is impractical because the composting systems are based on the principle of dry handling. The maximum moisture content, therefore, is predicated on the ability of the composted material to be stacked. The optimum moisture content for greatest decomposition should be maintained between 50 and 60% (wet weight). Moisture content above 60% causes compaction of the material and also fills the voids with water, thus reducing the amount of air present. This may cause anaerobic conditions to occur, giving off foul odors and slowing down the decomposition process.
If this occurs, it is necessary to mix the compost in order to supply oxygen and restore the process to aerobic conditions.
Under aerobic conditions, it is also important for the composted material to form interstices which entrap air when the windrow is formed or the material is mixed. If these spaces are filled with water, no oxygen is available to the organisms. If composting is to be done anaerobically, a high moisture content is a desirable condition and can be obtained by saturating the windrow before sealing.
If the moisture conent falls below 50%, high temperatures occur in the center of the pile. The high temperatures begin to destroy the microorganisms, seriously curtailing the decomposition process. The problem can be corrected by adding water to the organic matter to raise its moisture content.
Ingredients to Avoid
Organic material that should not be included in a compost pile
1. Residue from crops that have been sprayed with pesticides or herbicides;
2. Material diseased with rusts and viruses;
3. Meat scraps from the kitchen unless the compost heap is well protected from flies and vermin;
4. Material with hard prickles or thorns;
5. Persistent perennial weeds, to avoid any chance of these weed spreading they should be killed. Burning or spreading out in the sun so that they dry out completely is two methods for achieving this.
Materials, which definitely should not find their way into your heap include all metals, rubbers, glass and plastics - even so - called biodegradable plastic will endure for many years. Large quantities of newspaper and cardboard will greatly slow the rotting process. Also inadvisable is diseased plant material, such as brassica stalks infected with club root, or white rot on onions, leeks or garlic. Potato blight, however, can be safely composted. If your heap does not meet these criteria it is safest to burn suspicious material.
As indicated earlier, temperature is a key environmental factor and indicates the amount of biological activity taking place. The temperature within a compost pile is affected by moisture content, oxygen availability, and microbial activity.
A drop in the temperature may indicate the material needs to be moistened or aerated or that the decomposition is in a late stage of activity. Figure 2 illustrates that the speed of the process increases with increasing temperature from ambient to 350 C. The process is at its peak efficiency between 350C and 550C. As the process exceeds 550C, efficiency begins to drop abruptly and becomes negligible at temperatures in excess of 700C. At temperatures above 650C, sporeformers begin to lose their vegetative ability and form spores, resulting in very little activity. As the process cools from 650C or 700C back to 400C and lower, mesophilic organisms reappear in large numbers, establishing a high level of activity. Temperatures in anaerobic composting systems range from 380 C to 550 C, foul odors are given off, and pathogens may survive.
Oxygen is essential to maintain aerobic conditions. An ample supply of atmospheric oxygen throughout the compost pile at all times is necessary. Oxygen can be incorporated into windrows by turning or by thoroughly mixing with mechanical means. The windrow should be turned once every 3 to 4 days to maintain aerobic conditions.
Oxygen is added to enclosed digesters through continuous tumbling, stirring action, or through forced aeration. It is difficult to determine the true oxgen requirement because it is influenced by temperature, moisture content, and the bacterial population. It may be done by using the chemical oxygen demand (COD)Â as a means of measurement. Figure 3. The curve shows that at very low aeration rates, the oxygen supply is limiting and decomposition is anaerobic. Digestion under these conditions is relatively slow with little heat being produced.
With increased aeration, the process becomes anaerobic with a corresponding rise in temperature to a level, which restricts microbial activity. In this range, the capacity of the air to remove the excess heat is insufficient and the process becomes temperature limiting. As the compost begins to cool, water is removed faster than it is produced. In this range, decomposition is limited by the availability of nutrients.
If aeration rates are too high, heat will be removed faster than it is produced. This will lower the temperature below the thermophilic range, thus making the process under these conditions temperature limiting.
During the decomposition process, changes in pH occur. At initial stage the material is slightly acidic because as composting proceeds, acid-forming bacteria cause the compost to become more acidic, thus lowering the pH.
The microbes in the compost then begin to metabolize the inorganic nitrogen to ammonium nitrogen, causing the pH to rise rapidly. At this stage the compost becomes alkaline. As decomposition continues, the ammonia may be released to the atmosphere or converted to nitrates. The nitrates are lost by leaching or by denitrifying bacteria, rendering the compost nearly neutral or slightly alkaline.
Microbes Involved in Composting
Activators of Biodegradation
Animal manure is used to enhance the heating process; it must be fresh rather then already rotted. Fresh manure activates by seeding the heap with bacteria. If enough is added it will also bring a lot of heat into the compost heap. This can be very useful in winter when it is cold and there is a shortage of green matter to engender heat.
The right bacteria can also be introduced by addition some of last timeâ€TMs compost as the heap is constructed. Commercial activators are unnecessary if the above conditions are met, but you might find it interesting to experiment with herbal products, which definitely make a difference. Packaged bacterial activators are also available but since the types of bacteria at work vary with the temperature, air conditions and other factors, these may be of limited use.
Composting is the conversion of biodegradable organic matter to a stable product called humus. The microbes involved include bacteria, fungi, and actinomycetes. During aerobic composting there is a continual change in the qualitative and quantitative nature of the microbial population. At first, fungi and acid-producing bacteria appear, causing the temperature to rise (mesophilic range). When the temperature rises above 400 C, these microbes are replaced by thermophilic bacteria, actinomycetes, and thermophilic fungi.
Transformation of biological material is carried out by microbial flora. They requires moisture, heat and, depending on the type of production operation chosen, air. A single gramme of compost will contain up to a billion bacteria, 100 million actinomycetes, a million fungi, algae, protozoae and others in their hundreds of thousands. Moreover, different bacteria with differing skills take over, depending on whether the heap is an aerobic (air-using) or anaerobic (airless) production line, the temperature, the pH level and the mineral content. Bacteria utilize nitrogen to break down the carbon materials and form compost.
Bacteria : Both mesophilic and thermophilic bacteria play an important role in the composting process. The mesophilic bacteria predominate during the initial and final phases of decomposition when temperatures are below 400 C. At initial stage, large numbers of aerobic mesophilic bacteria are present. They begin to multiply rapidly and sue to their increased biological activity they generates heat and temperature within the composting pile is increased. As the temperature rises above 400 C, the mesophilic bacteria (the exact role of mesophilic bacteria is not fully understood) are replaced by the thermophilic bacteria which continue to generate heat. Thermophilic bacteria, protein, lipids, and the noncellulose carbohydrate are the fractions of the compost. They are not capable of breaking down cellulose and lignin. At this stage, temperature is rasied up to 700 C. The range of temperature from 400 to 700 C is known as the thermophilic range. The rise in temperature is influenced to a great extent by oxygen availability.
Actinomycetes : They exist in the thermophilic region and they utilize hemicellulose but not cellulose. Thermophilic actinomycetes are capable of decomposting cellulose. Thermophilic actinomycetes can grow at temperatures up to 72oC and, therefore, dominate the microbial population at the highest temperature level during the composting process and within the thermophilic range, the growth rate of action-mycetes increased 500-fold as compared to only a 5-fold increase for bacteria.
Fungi: They appear in both the mesophilic and the thermophilic stages of composting the mesophilic fungi utilize the simple carbon substrates as their source of food. During the late stages of decomposition they utilize some cellulose and hemicellulose. Thermophilic fungi are less temperature tolerant than the thermophilic bacteria or actinomycetes. They operate in the range of 40oC to 60oC. Above 60oC, thermophilic fungi will die off. Mesophilic fungi (similar to like mesophilic bacteria) are active during the initial and final phases of decomposition. As the compost heats up above 40oC, the mesophlic fungi are replaced by thermophilic fungi. As the temperatures in the compost pile rise, both the mesophilic and the thermophilic fungi migrate to the outer edges of the compost pile where lower temperatures exist. When the temperatures drop, the fungi migrate throughout the pile and reappear in large numbers.
EFFECT OF ORGANIC FERTILIZERS IN PONGAMIA PINNATA
Pungam is extensively used for afforestation of watersheds in the drier parts of the country. It is drought resistant, moderately frost hardy and highly tolerant to salinity. It is being propagated by direct sowing or by transplanting one-year-old seedlings raised in nursery.
Microorganisms that are used as biofertilizers stimulate plant growth by providing necessary nutrients as a result of their colonization at the rhizosphere (Azotobacter, Azospirillum, Pseudomonas, phosphatesolubilizing bacteria, and Cyanobacteria) or by symbiotic association (Rhizobium, mycorrhizae and Frankia). The role of biofertilizers has already been proved extensively in annual crops, but its exploitation in perennial trees in India is scanty. In forestry, few research reports are available to demonstrate that biofertilizers stimulate the growth, biomass, nodulation and VAM-colonization. Keeping this in view, the present study was designed to elicit information on the effect of biofertilizers on the growth and development of pungam (Pongamia pinnata) (L.) Pierre.
Material and Methods
The study was carried out at Forest College and Research Institute (11o19 â€˜N, 76o56 â€˜E, 300 above MSL). Six-month-old uniform sized seedlings were chosen for biofertilizer inoculation. The seedlings were transplanted in 30x45 cm polybags filled with nursery mixtures of red soil, sand and FYM (2:1:1). The experiment was set up in a completely randomized design and replicated thrice. The nursery soil mixture of the polybags were inoculated with biofertilizers, viz., (i) Rhizobium, (ii) phosphobacteria, (iii) Vesicular-Arbuscular Mycorrhizae (VAM), (iv) Rhizobium+phosphobacteria, (v) phosphobacteria+VAM, (vi) Rhizobium+VAM, (vii) Rhizobium+ phosphobacteria+VAM. Uninoculated seedlings were maintained as control.
Biofertilizer inoculation was prepared with a base of peat soil. Two hundred grams of Rhizobium and phosphobacteria were weighted and mixed with 3 kg of well decomposed and powdered FYM separately. Fifty grams of this inoculum mixture and twenty grams of VAM inoculum were applied to each polybag at 5cm depth near the root zone.
Six seedlings in each treatment were selected at random and observed initially, 2 and 4 months after inoculation for number of leaves, leaf area (LICOR Model LI 3000 Leaf Area Meter), root volume, total dry matter, DGR, NAR, CGR, number of nodules and VAM colonization. The results were subjected to analysis of variance and tested for significant differences (P