eChapters

Organic C in agricultural soils contributes positively to soil fertility, soil tilth, crop production, and overall soil sustainability. Changes in agricultural management can potentially increase the accumulation rate of soil organic Cd (SOC), thereby sequesteringCO₂fromtheatmosphere.Optimizingagricultural management for accumulation of SOC can result in the sequestration of atmospheric CO₂, thereby partially mitigating the current increase in atmospheric Carbon dioxide. In addition to the environmental benefits of soil C sequestration, Carbon dioxide consideration has also been given to the implementation of a C credit trading system which may provide economic incentives for C sequestration initiatives.

Changes in agricultural practices for the purpose of increasing SOC must either increase organic matter inputs to the soil, decrease’decomposition of soil organic matter (SOM) and oxidation of SOC, or a combination thereof. These practices include, but are not limited to, reducing tillage intensity, decreasing or ceasing the fallow period, using a winter cover crop, changing from monoculture to rotation cropping, or altering soil inputs to increase primary production (e.g., fertilizers, pesticides, and irrigation). Implementing practices that sequester C can reverse the loss of SOC that may have occurred under intensive cultivation thereby increasing SOC to a new equilibrium

A nutrient budget is a valuable indicator of the long term sustainability of a cropping system. It indicates where fertilizer application is inadequate and leading to decline in the soil nutrient status. Conversely, it can indicate excessive inputs which result in a nutrient surplus and greater potential for losses to the environment and waterways. (Combs et al., 1996) Thus nutrient budget is the comparison between all the sources of nutrients available to the producer and the requirement of nutrients to meet the crop and soil needs. The sources can either be from on the farm, such as livestock manure or credits from legumes, or from off the farm, such as purchased fertilizer or irrigation water. The requirement is the amount of nutrients needed by the crop to obtain the expected yields.

Most values for nutrients available from different sources (credits) and crop nutrient requirements are calculated from estimates taken from many years of long historical averages and field research. There is no “real time” method of calculating exactly what neither the crop’s nutrient requirement or the nutrients available are at any one time. More closely, both the nutrient requirements and availability are based on past performance for the climatic and soil condition. These values are given with some surety that the crop grown will be supplied with adequate nutrient during the growing season and the crops will not be limited in its growth. All incidental environment losses, such as runoff and leaching, have been accounted for. Climatic conditions, particularly temperature and soil moisture, greatly influence both the crop performance and the soil’ s capacity to provide nutrients to the plant. During any growing season, there can be many changes in the climate conditions that will affect both the crop growth and soil delivery of nutrients to the crop.

Although a nutrient budget is not an exact formula for supplying nutrients, it is one method for organizing the nutrient needs ofthe crop with the nutrients available on the farm. Nutrient budgets can easily determine if there is a gross imbalance between the nutrients that are available vs. the amount required. Nutrient budgets are one of the best methods to see the over all supply of crop nutrients available, compared to the estimated crop needs as given by historic records and field research. Continued use of soil testing, plant and water analyses and yield monitoring are essential to maintain good nutrient balance with desired results.

Biodiversity is the variety of life in different microbes, animals, plants and their genes present in the ecosystem. Soil provides a vital habitat and environment primarily for microflora such as bactria, actinomycetes, fungi as well as microfauna viz. protozoa and nematodes, mesofauna such as microarthopods, enchytraeids, macrofauna such as earthworms, beetles, termites and millipedes (Gaur 2006a).

Biodiversity and soil are interlinked which interact closely with wider biosphere. Conversely, biological activity is ofprime importance in influencing the physical and chemical conditions of soil (Bardgett 2005). The level of soil biological activity is, therefore, affected by soil type and also depends on the use of management practices which contribute to crop productivity.

Soil biodiversity and soil processes

A majority of soil organisms participate in various processes which are essential for the biosphere. The main ecological function is to decompose organic matter largely derived from the plant and animals residues Which consist of celluloses, hemicelluloses and lignin, and to supply plant nutrients to support growth. These organisms participate in various nutrient cycles and processes such as nitrogen mineralization, nitrification, nitrogen fixation, transformations ofphosphorus, potassium, sulphur, calcium, magnesium, iron and micronutrients (Pankhurst et al 1997). They participate in bioremediation of harmful compounds such as heavy metals and pesticide residues (Gaur 2006 b). They not only maintain physical and chemical conditions of soil, but also regulate emissions / assimilations of green house gases and suppress soil borne diseases and pests

Rice-wheat cropping system is the most important food production system in India. This system has enabled the country to attain food security during last three decades and provided livelihood to millions of farming families in recent times. The productivity of this system has now started showing signs of decline or stagnation at many places. There are also concerns of declining soil health and other related environmental problems. At the same time, food demand is rapidly increasing due to increasing population and income growth. During the past 30 years, agricultural production has been able to keep pace with population demand for food. This came about through significant area and yield growth. Area growth was a result of new lands being farmed and through increases in cropping intensity, from a single crop to double or even triple crops per calendar year. Area growth will be less important in its contribution to production growth in the future as more land is used for urban areas and industry. Yield growth will have to be the mainstay for providing the means for meeting future food demands unless food imports start to play a major role. Total factor productivity is declining and farmers have to apply more fertilizer to obtain the same yields. There is, therefore, a huge challenge ahead to meet future food demands without damaging the natural resource base on which agriculture depends, producing food at a cost that is affordable by the poor, and with incentives to farmers that allow them to improve their livelihoods. Water will become a major limiting factor for sustained production in the next decade. Rapidly growing urban areas and industry will compete with agriculture for good quality water. There are already reports of declining water tables in some areas leading to more costly pumping of groundwater and increased costs of production.

This chapter describes various conservation agriculture technologies to attain the goal of increasing productivity and meeting food security needs while at the same time efficiently using natural resources, including water, providing environmental benefits and improving the rural livelihoods of farmers. The major success in the last few years has been the development and deployment of conservation agriculture technologies (CATs) with farmers in the rice-wheat systems. CATs range from simple surface seeding, where wheat seed is broadcast on the non-ploughed soil; no-till with a special opener for placing seed in the soil also without ploughing; reduced tillage and bed planting. This has benefited farmers through less cost, more yields and more income. CATs are defined as any practice that will result in improvement of the efficiency of natural resources. These technologies are rapidly gaining popularity among farmers as they result in higher production at less cost with significant benefits to the environment and more efficient use of natural resources. This ultimately results in higher profits, cheaper food, and improved farmer livelihoods. Crop diversification is also easier as less land is needed to produce staple cereals, freeing up land for other crops.

Agriculture in India is one of the most important sectors of its economy. It provides livelihood to almost two thirds of the work force in the country and accounts for 18% of India’s GDP. About 43 % of India’s geographical area is used for agricultural activity and large number of production systems are in practice in different parts ofthe country. In pre-independence era (before the 1950s), agriculture in India was a system of harnessing nature for the sustenance of human beings, similar to the presently defined organic farming. Some countries have moved away from inorganic to organic farming yet it is not possible for India to depend entirely upon this system of farming due to large population. Total availability of plant nutrients from organic sources is projected to be 7.75 million tonnes by 2025 (Tandon, 1997) against the total requirement of37.50 million tonnes (Katyal, 2001) for 1504 million population (Sekhon, 1997). Thus nutrients supply through organic sources alone would result in deficiency of about 30 million tonnes of nutrients. Hence, it is imperative to use both organic and inorganic sources of plant nutrients enhance food production for the increasing population (Mahajan et al., 2007). In India the contribution of organic sources was 80-100 per cent in 1949-50 and reduced to about 32 per cent in 1993-94 and 20-25 per cent in 2004-05. So, it is imperative to enhance organic sources to meet total nutrient consumption. Following independence, rapid population growth in India placed great pressure on land and on these traditional farming systems; huge demands for food grains led to increased use of fertilizers and pesticides to boost production. Still a negative balance of about 8 million tones of NPK is foreseen in 2020, even if we continue to use chemical fertilizers, maintaining present growth rates of production and consumption. The most optimistic estimates at present, show that only about 25-30 per cent nutrient needs of Indian agriculture can be met by utilizing various organic sources. Many of the gains in production during the last 4-5 decades resulted from the “Green Revolution,” a campaign of technological interventions in agriculture widely adopted by farmers in developing countries. Expansion of irrigation to cover rain fed areas, popularization of hybrids/ transgenic varieties of crops, and use ofsynthetic chemical fertilizers and pesticides were the maj or technologies promoted. This paid rich dividends in India, quadrupling food grain production from 50 million metric tons in 1950-51 to 211 million metric tons in 2001-02, and enabling India to become self-sufficient in food grain. Now a second green revolution is also in the offing, to boost agricultural production and meet the estimated requirement of 337 million metric tons.

Indian horticulture has shown impressive impact on production, productivity and profitability. Currently, the total production of horticultural produce is 214.7 million tones from the 9% of total cultivated area in India, which contribute 30.4% to GDP of agriculture (Singh, 2010). In world perspective, India is second largest producer of fruits (68.5 mt) from 6.10 m ha area and contributes 11.2% in global fruit production. Vegetable crops occupying 8.0 m ha have the production of 129.1 mt (Table 1). However; India is the largest producer, consumer and exporter of spices and spice products in the world and produce more than 50 spices. The spice production in India is the order of 4.14 mt from an area of about 2.63 m ha. India is also the leading producer of plantation crops in the world and contributes 22.34% in coconut, 25% in cashewnut and 55% in arcanut. Commercial floriculture sector has recorded fast pace of growth during the last decade. During the last decade area under floriculture has expended to 1,67,000 ha with production of 9,87,000 MT of loose flower and 4.8 million cut flowers (Singh, 2010). The over all percent share of fruits and vegetables to their total production and contribution of different states for production of fruits and vegetables are repicted in Fig. 1 & 2. From the above fact, it is indicated that the production of horticulture produce has increased manifold but the gap in demand and supply continues simultaneously and is hardly sufficient and meets only 46% of national demand. Hence, there is a strong need to increase the production and productivity through crop diversification.

Protected cultivation of horticultural crops offers the best choice for diversification from traditional agriculture production system for a number of reasons. Production of crops under protected structures has great potential in augmenting production and quality of vegetables, flowers and in some fruit crops in main and off-season and maximizing water and nutrient use efficiency under varied agro-climatic conditions of the country. This becomes relevant to growers in India who have small land holding. They would be interested in a technology, which helps them to produce more crops each year from their land, particularly during off-season when prices are higher. The commonly protected structures are polyhouses, poly-tunnels, floating row covers, clotches, shade-net, insect-proof net and plastic-mulches (Chandra et al., 2000 ; Singh et al. 2010). These protected structures act as physical barrier and play a key role in integrated pest management by preventing spread of insect-pests and viruses which causes severe damage to the crop (Singh et al., 2003). This technology has great potential especially in periurban agriculture in near future, since it can be profitably used for growing high value vegetable crops like tomato, cheery-tomato, coloured peppers, parthenocarpic cucumbers, cut-flowers like rose, carnation, Berbera, lilium and fruits like strawberry, grapes etc. and for off-season cultivation of vegetables and their healthy and virus-free seedling production.

Protected cultivation is intended to mean some level of control over plant micro-climate to alleviate one or more of abiotic stresses for optimum plant growth. The microclimatic parameters being referred here are temperature, light, air-composition and the nature of rooting medium.

India is a leading vegetable producing country in the world. Presently it occupies 7.981 million hectare area with the annual production 129.077million tones (2008-09). The country being belessed with the unique gift of nature of diverse climate and distinct seasons, make it possible to grow an array of vegetables number exceeding more than hundred types. However, potato being the staple food and easy to mix in several preparations ranks first (26.6%) in total production of vetetables followed by onion (10.5%) and other important Solanaceous vegetables like tomato (8.6%), brinjal (8.0%). Cauliflower and cabbage are most preferred winter vegetables and their total share in the country’s vegetable production is 5.1 and 5.3%, respectively. Other important vegetables, which are primarily grown in the country, are okra, onion, vegetable peas and a good range of cucurbits (Fig. 1)

There is miss-match in area production and productivity of vegetables among various states of the country. The West Bengal ranks first in the total production of vegetables in the country and its production during the year 2008-09 was in tune of more than 22.704 million tones, contributing the more than one-fifth of total country’s vegetable product ion. Uttar Pradesh, Bihar and Orissa in north India and Maharashtra, Tamil Nadu and Karanataka in south India are the other leading vegetable producing states in the country. In last one decade, there has been considerable progress in enchancing the productivity of vegetables which is presently 16.2 tonnes hectare^-1. Incessant growth of urbanization, ceaseless fragmentation ofland holdings and depleting natural resources are the major challenges before the expansion of any agricultural commodity either cereals or vegetables. Hence, our attention must be focused on vertical expansion strengthened with the boon ofthe technology instead of horizontal expansion just by increasing the crop area. To ensure the nutrition security of the burgeoning population of the country, it is estimated that up to 2020, the country’s vegetable demand would be around 155 million tones (Rai et al., 2004; Pandey et al., 2009). To achieve this target, it is sine qua non to integrate the various technologies right from production to post-harvest.

The apparent reasons for undesirable productivity under intensively cultivated areas are depletion of native nutrient reserves, emergence of multinutrient deficiencies, and consequent decline in factor productivity of applied nutrient (Dwivedi et al., 2006; Yadav, 1998; Yadav, 2003). Surveys conducted at PDFSR in different agro-climatic regions of Indo- Gangetic Plain indicated that in order to achieve previously attained yield levels, farmers have started applying greater doses of N than the recommended ones (Dwivedi et al., 2001; Sharma, 2003). Such indiscriminate use of N is likely to further worsen the nutrient imbalance in soil-plant systems, besides increasing the pest incidence, cost of production and environmental problems (Dwivedi et al., 2001). The annual productivity of rice - wheat could hardly exceed 9 t ha^-1 in the multilocation experiments on yield maximization (Dwivedi and Singh, 2011). On the other hand, long-term experiments (Singh and Mishra, 2010) and other studies indicate that crop productivity can be sustained with balanced fertilization, taking into account the emerging deficiencies of secondary and micronutrients (Tiwari et al., 2006)

Nutrient management is a major component of a soil and crop management system. It becomes even more important in intensive high yielding cropping systems because of the higher investments at stake. The SSNM is applying those concepts to areas within a field that are known to require different management options from the field average. Site specific nutrient management is a concept that can be applied to any field and any crop. Yet, it is most often thought of in relation to use of computer and satellite equipment, and does not require large farming operation. The technology tools certainly expand the capabilities for using site-specific management. This is really a “repackaging“ of management concepts that have been developed and promoted for many years.

Soybean [Glycine max (L.) Merrill] is the leading oilseed crop in the world. Its area and production are far ahead of other oilseeds at the global level (Table 1). The commercial cultivation of this crop in India started in the early 1970’s. Within a span of 4 decades its spread has been phenomenal and today it occupies around 9.67 million hectares with a production of about 10.22 million with an average productivity of around 1006 kg ha^-1 (DSR, 2010) (Table 2). It is now the fourth largest among field crops after rice, wheat and maize (GOI, 2007) in India and has become the leading oil seed crop surpassing groundnut and mustard and rapeseed. It is contributing nearly 37% to the total oilseeds produced in India. The central India comprising the states of Madhya Pradesh, Maharashtra and Rajasthan account for more than 95% of the total area under this crop. Chhattisgarh, Karnataka, Andhra Pradesh, Uttar Pradesh etc account or the bulk ofthe rest ofthe area. It is predominantly a rainfed crop with only about 3% of the total area getting some assured irrigation facility. Further, it is concentrated in areas which receive lesser rainfall in its early vegetative phase. A large number of crops have been replaced by soybean to a variable extent in its march towards achieving its present position. Badal et al. (2000) have reported that a large number farmers switched over to this crop from sorghum, groundnut, maize, cotton etc in the state of Madhya Pradesh owing to greater yield potential even under adverse conditions (Table 3). Further, it has become an integral part of several cropping systems including both intercropping and-sequential cropping systems in different parts of the country.

The population of India is estimated to touch 1.4 billion by the year, 2025, which will need at least 300 million tonnes of food grain. This necessitates the production of additional food grain from the same land without loosing the production potential of the soil. This, in turn, requires extensive research to provide a scientific basis for enhancing and sustaining food production as well as soil productivity with minimum environmental degradation. In order to attain this it is essential that the amount of nutrients removed from the soil should be replenished through judicious use of fertilizers and manures. This needs a more comprehensive approach for fertilizer use, incorporating components like soil test, field research and economic evaluation ofthe results. Soil testing is one of the best scientific means for quick and reliable determination of soil fertility status. Soil test crop response study in the field provides soil test calibration between the level of soil nutrients as determined in the laboratory and the crop response to fertilizers as observed in the field for predicting the fertilizer requirements of the crop.

Objectives of soil testing.

Soil testing provides a sound information about the suitability, fertility and productivity of the soil. This enables the farmers to make the most profitable use of some of the costly inputs in farming. However, lack of information among the farmers about soil testing and their importance in management of resources necessitates that the work of soil testing should be taken extensively. Soil testing is a useful tool for making fertilizer recommendations for various crops and cropping sequences as well as reclamation of problem soils. Thus the major objective of soil testing are to identify the type of soil related problems like salinity, alkalinity, and acidity and to suggest appropriate reclamation/amelioration measures and to evaluate the fertility status in terms of available nutrients for making soil test based fertilizer recommendations.

Oilseeds serve as rich source of food, feed, energy, employment and commerce. The productivity of oilseeds in India (1006 kg ha^-1 during 200809) is very low when compared with the world productivity (1878 kg ha^-1 during 2008). The oilseeds production in the country often sufers from a high degree of variation in annual production owing to their predominant cultivation under low and uncertain rainfall situations which is further handicapped by input starved conditions with poor crop management. Nutrient and water are the key inputs for crop production. Improving efficiency and factor productivity under complexities of diminishing quality resources and increasing ecoawareness are critical for sustainable oilseeds production.

The vegetable oils consumption in the country is steadily rising and has sharply increased in the last couple of years touching around 14.1 kg head^-1 year^-1 during 2009-10. As per DAC-Rabo Bank, India’s per capita consumption is likely to reach at least 16.38 kg year^-1 by2020 and for a projected population of 1331 million, vegetable oil requirement will be 21.8 million tonnes. This is equivalent to about 66 million tonnes of oilseeds assuming that there is no change in the proportion of different oilseeds produced in the country in the next ten years. Assuming about 20% of vegetable oils contribution from sources like ricebran, cotton seed, coconut, oilpalm, etc., still the country needs to produce about 55 million tonnes of oilseeds by 2020. Considering that the oilseeds production during 2008-09 was just 27.56 million tonnes, the country needs to double oilseeds production in next 10 years requiring a growth rate in excess of 6%

Rice-wheat is a dominant cropping system in the Indo-Gangetic Plains covering approximately an area of 10.5 million ha. Modern agricultural production practices have emphasized the widespread use of fertilizers as a source of nutrients. The continuous use of high levels of chemical fertilizers over a prolonged period, decline in area under legumes and reduction in the use of organic manures has resulted in soil degradation and environmental pollution. It is estimated that the gap between nutrient removal by crops and addition through fertilizers in India will remain at level of 8-10 million tones per annum. Such negative nutrient balances are depleting the soils of their nutrient reserves resulting in acute deficiencies of nutrients. Integrated plant nutrient supply (IPNS) is an important component of sustainable agricultural intensification. The goal of integrated nutrient management (INM) is to integrate the use of all natural and man-made sources of plant nutrients, so as to increase crop productivity in an efficient and environmentally benign manner, without diminishing the capacity of the soil to be productive for present and future generations. The INM is made up of components which possess great diversity in terms of chemical and physical properties, nutrient release efficiencies, positional availability, crop specificity, and farmers’ acceptability. Since organic manures cannot meet the total nutrient needs of modern agriculture, integrated use of nutrients from fertilizers and organic resources seems to be a need of the time. For INM to make desirable progress and find wide acceptance, nutrient supply packages for important agroecological environments need to be developed. These should be technically sound, practically feasible, economically attractive and socially acceptable. Integrated plant nutrient systems can ensure long-term sustainability of agricultural growth through improvement in soil health and will significantly reduce the needs for chemical fertilizers. The complementary use of chemical fertilizers and organic fertilizers may increase the efficiency of chemical fertilizers in order to maintain a high level of crop productivity. Because of low primary nutrient content and thus the need for large applications per unit area, farmers and policy makers are often reluctant to adopt and promote the use of organic fertilizers. The different components of INM possess great diversity in terms of chemical and physical properties and nutrient release patterns.

Food security, nutritional security, sustainability and profitability are the main foci ofpresent agricultural scenario in India. In the absence of additional land for bringing under plough vertical growth in agriculture through intensive cropping and enhanced productivity becomes inevitable. Intensification of agriculture to meet the growing needs of the burgeoning population has brought with it numerous productivity related constraints. It has triggered multiple nutrient deficiencies in soil and this has raised doubts on the soils capacity to sustain anticipated production levels. One of the key inputs in enhancing and maintaining the productivity ofintensified agricultural systems is chemical fertilizer which provides nutrients in readily available form. But long term experiments on various cropping systems at various agroecological regions and soil types revealed that continuous use of chemical fertilizers in unbalanced and indiscriminate manner deteriorates the soil health and leads to deleterious effect on long term soil fertility and yield sustainability. Apart from the soil productivity issue, the use of chemical fertilizer is also becoming more and more costly due to scarcity during peak demand. The excessive use of chemical fertilizers is not only costly but they pollute the production environment (Singh et al., 2005; Dwivedi et al., 2003).

In the coming decades, a major issue in designing sustainable agriculture system will be the management and rational use of organic inputs such as animal manure, green manure, crop residues and biofertilizers etc. (Powlson, 1994). Long term studies indicated that current fertilizer recommendations are inadequate for maintaining yields (Bhandari et al., 2000; Singh and Mishra, 2010; Tiwari et al., 2006). It is, therefore, to sustain high crop yield without deterioration of soil fertility it is important to apply required amount of plant nutrients through fertilizers in combination with organic sources, crop residues, biofertilizers etc.

Post independence era brought about a radical change in agricultural scenario which improved economy and living standard of Indian farmers to a great extent. Green revolution, (field crops) during early sixties followed by white revolution (milk) and thereafter yellow (oilseeds) and blue (fish) revolutions made the country not only self sufficient in most of the food commodities but also exporter in many. Several calamities including droughts, floods, and ill effects of national and international conflicts faced by the, people of the country during post independence era could not affect the economy and stability of the country much because of rich agricultural heritage. As usual, the rapid and rather un-planned development creates several problems and this was true in our conditions too. Loss ofindigenous land races, depletion of soil nutrients and water resources, creation of salinity and water logging, resurgence of pest and diseases, declining factor productivity and farm profits and increased environmental (air, water & soil) pollution are among such problems have great concern to agricultural scientists and planners in coming future. The situation further aggravated because of industry oriented government policies and globalization which supported growth of industries and trades rather than agriculture and hence the growth rate in these sectors was considerably high. This fact is more visible by the figures on relative contribution of different sectors in the national GDP during last sixty years (Table 1). At the time of independence of the country more than 75% people were depend on agriculture related occupations which came down to mere 67.4% in 2009-10. Similar is the case of total contribution of agriculture in national GDP which decreased from 57% in 1951-52 to as low as 14.6% in 2009-10. Besides government policies, major factor identified responsible for degradation of resources, stability in production and decreased factor productivity is chemical based farming and that too in imbalanced and improper methods of application practiced by the farmers for getting more andinore production and profits per unit area per unit time The solution of this lies in the increased use of organic sources of nutrients in proper ratio along with chemical fertilizers - IPNS (Integrated Plant Nutrient System). Livelihood of marginal and small land holders who represent a large section (more than 86%) of farming community and remained deprived of advancements in the, field of agriculture has been the main agenda of the Indian Government in Xlth, five year plan and to continue in Xllth plan too. To ensure livelihood improvement with focus on small and marginal farmers Integrated Farming System (IFS) has been proved to be an effective approach. Accordingly, the Project Directorate of Cropping Systems Research renamed as Project Directorate for Farming Systems Research with AICRP on Integrated Farming Systems Research and Network Project on Organic Farming mandated with farming systems perspectives. Since, integrated farming system is a holistic approach wherein all the wastes and residues are recycled within the system and nothing go waste. Output of one enterprise is used as input for the others. This way, farming becomes more economic and environmentally safe.

Sustainable agriculture warrants a wise management of natural resources and inputs to satisfy human needs in the fast changing scenario while maintaining, if not improving, the quality of environment. Soil as a natural resource is facing more and more serious degradation threats under modern agriculture. Incidence and expansion of multi-nutrient deficiencies in Indian soils owing to inadequate and unbalanced nutrient input through fertilizers is considered one of the major reasons for decline in factor productivity of crops. The problem of soil fertility depletion is spectacular across the soil types and agro-climatic zones, but it is more acute in intensively cropped areas, where annual nutrient removal by the crops often far exceeds replenishments. Recent diagnostic surveys indicate that in several high productivity areas of irrigated ecosystems like, Trans-and Upper Gangetic Plain zones, farmers are resorting to even excessive use of fertilizers, especially N, to maintain the yields at levels attained previously with lower fertilizer application rates. With an unabated deterioration in soil health in general, and soil fertility in particular, and a mounting pressure on finite land resources due to increase in population, the interest in soil fertility and soil health has revived due to several reasons:

Stagnation in growth rates of production and productivity of staple foodgrains - threat to food security

Decline in factor productivity, thus increasing cost of production

Nutrient withdrawals in excess of replenishment

Low nutritional value of food and feed grown on nutrient-starved soils - threat to nutritional security

Poor quality of produce fetching low price - threat to economic security

Limited availability of additional land for crop production, along with declining yield growth for major food crops, have heightened concerns about agriculture’s ability to feed a world population expected to exceed 7.5 billion by the year 2020. Decreasing soil fertility has also raised concerns about the sustainability of agricultural production at current levels. Future strategies for increasing agricultural productivity will have to focus on using available nutrient resources more efficiently, effectively, and sustainably than in the past. Management of the nutrients needed for proper plant growth, together with effective crop, water, soil, and land management, will be critical for sustaining agriculture over the long term. Plants, like all other living things, need food for their growth and development. Growth is the function of various factors like light, carbon dioxide gas, water and mineral nutrients. Plants require 16 essential elements. Carbon, hydrogen, and oxygen are derived from the atmosphere and soil water. The remaining 13 essential elements (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, manganese, copper, boron, molybdenum, and chlorine) are supplied either from soil minerals and soil organic matter or by organic or inorganic fertilizers. For plants to utilize these nutrients efficiently, light, heat, and water must be adequately supplied. Cultural practices and control of diseases and insects also play important roles in crop production. Each type of plant is unique and has an optimum nutrient range as well as a minimum requirement level. Below this minimum level, plants start to show nutrient deficiency symptoms. Excessive nutrient uptake can also cause poor growth because of toxicity. Therefore, the proper amount of application and the placement of nutrients are important.

All the states have some area under irrigation. Thus the term ‘irrigated ecosystem’is rather loosely defined, and the states having distinctly large net irrigated area may constitute this ecosystem. Two such areas can be easily carved out i.e., Indo-Gangetic Plain region representing five states namely Punjab, Haryana, U.P., Bihar and West Bengal, and coastal areas of two southern states i.e., A.P and Tamil Nadu. About 56% of the net irrigated area of the country exists in these states, and the cropping intensity is also much higher (144%) as against national average of 132%. With demographic viewpoint also, these areas are densely populated. Of late agriculture in this ecosystem has become unsustainable owing to over-exploitation of natural resources. Studies have conclusively established the superiority and worth of integrated nutrient management in restoration of soil health and sustenance of crop productivity and profits.

The basic concept underlying the principles of integrated nutrient management (INM) is the maintenance, and possibly improvement, of soil fertility for sustaining crop productivity on long-term basis. This may be achieved through combined use of all possible sources of nutrients and their scientific management for optimum growth, yield and quality of different crops and cropping systems. INM is not a new concept, but an age-old practice. Its importance was, however, not realized earlier due to low nutrient turn over in soil-plant system and almost all the nutrient needs were met through organic sources, which supplied secondary and micronutrients also besides major nutrients. INM has now assumed great significance mainly because of two reasons. First, the need for continued increase in agricultural production based on increase in per hectare yields requires growing application of nutrients, and the present level of fertiliser production in india is not enough to meet the total plant nutrient requirement. Second, the results of a large number of experiments on manures and fertilisers conducted in india and other countries reveal that neither the chemical fertilisers alone nor the organic sources exclusively can achieve the production sustainability under intensive cropping systems (Hegde and Dwivedi, 1993). Even the so called balanced use of chemical fertilisers would not be able to sustain high productivity due to emergence ofthe deficiencyofone ormore ofthe secondaryandmicronutrients (Swarup and Wanjari, 2000). The interactive advantages of combining organic and inorganic sources of nutrients in INM have proved superior to the use of its each component separately. The advantages of INM can be broadly enumerated as following:

Rice-wheat (RW) is the major cropping system occupying about 10.5 mha in the IGP of India. It contributes more than 60% of the foodgrains to the central pool. With shrinking land resources and burgeoning population, the RW system will be under pressure to produce more grain output per unit area in the coming decades. Meeting this challenging task requires sustainable management of soil, water and plant nutrient resources. High yields of the irrigated RW system result in production of huge quantities of crop residues. Total production of crop residues in Punjab is about 47.2 mt which includes paddy straw, wheat straw, cotton sticks, sugarcane leaves, maize stalk, and other oilseeds and pulse residues (Beri and Gupta, 2003). Wheat and rice straw constitutes more than 70% ofthe crop residues produced in the country. Paddy straw alone constitutes more than 50%. Cotton and sunflower residues are generally used as fuel. Sugarcane trash (leaves) is generally burnt in-situ or used as fuel after collection from the field. Increasing constraints of labour and time have led to the adoption ofmechanized farming in the highly intensive RW cropping system. Approximately 91% ofthe total rice area is mechanically harvested, while 82% of the total wheat area is mechanically harvested. Traditionally, wheat and paddy straws have been removed from the fields for use as cattle feed and for several other purposes such as livestock bedding, thatching material , for houses, and fuel. While more than 80% ofwheat residue is collected by the farmers after combine harvesting and often fed to animals, paddy straw is considered poor feed for animals due to its high silica content.

Substantial loss ofplant nutrients (especially N and S) and organic carbon occurs during burning of crop residues, with important implications to soil health. About 40% of the N, 60-85% of the K, 30-35% of the P, and 40-50% of the S absorbed by rice remains in the vegetative parts at maturity. One tonne of paddy straw contains approximately 6-7 kg of N, 1.0-1.7 kg of P₂O₅ and 14-25 kg K₂O. Apart from huge loss of precious plant nutrients, burning of crop residues depletes soil health. Air pollution from stubble burning also impacts human and animal health both medically, and by traumatic road accidents due to restricted visibility. In view ofthe serious problems associated with the residue burning, new ways are being sought to efficiently utilize the huge amount of surplus residues produced in the country.

With the advent of modern crop varieties, better irrigation facilities and greater use of fertilizers and other inputs country has changed within the last 50 years from a region of food scarcity to a region of food sufficiency. The greenrevolutiontechnologiesinvolvinggreateruseofsynthetic agro-chemicals such as frrertilizers and pesticides with adoption of nutrient- responsive, high yielding varieties of crops have boosted the production per unit area under different crops and cropping systems. However, this increase in production has slowed down and in some cases there are indications of decline in growth of productivity and production (Table 1). These production scenarios may be envisaged as corresponding decrease in soil organic matter and continuous increase in multi nutrient deficiency (Dwivedi et al., 2006). If such situation is allowed to continue for another few decades, there are chances that todays’ productive land may become unproductive. The declines in yield and production fatigue have been noticed in various cropping systems of different agro-eco region (Gill and Singh, 2009). Farmers’ participatory surveys conducted in Indo-Gangetic Plain (IGP) region indicates that farmers’have resorted higher doses ofnutrients each year to obtain the same yield as obtained in previous year (Dwivedi et al., 2001). The probable reasons behind these are continuous mining of nutrients, inadequate use of organic sources, imbalance fertilization and decline of soil organic matter.