Paper Number 2

Integrated nutrient management vis-à-vis crop
production/productivity, nutrient balance, farmer
livelihood and environment: India*

A. Subba Rao and K. Sammi Reddy
Indian Institute of Soil Science, Nabi Bagh, Berasia Road,
Bhopal - 462 038 (M.P.), India

1. Food security and livelihood in India

Food security is the most important factor that determines the survival of human kind. Without food security, a nation cannot expect better life for its people. Famines in India are “a nightmare of the past”. The green revolution witnessed in late 1960s has contributed immensely over the years to cereal production in India and hence a substantial increase in the net per capita availability of food grains was registered (Table 1). This has led to a nationwide sense of complacency that, in a way, slowed down the growth rate in agricultural production during 1990s, while the population continued to grow at a high rate. The net result was a decline in the per capita food grain availability in the terminal decade of 20^th Century. Even with present level of production, there is enough food in the country to meet energy and protein requirements of the current population, if the food were distributed equitably according to needs. But as we see, surplus production and widespread hunger coexist at the national level. At present, India alone accounts for one fourth of all world hunger. It is particularly ironic that there are 200 million food-insecure people in a country that currently bas buffer stocks of food grains in excess of 60 million metric tonnes.

Table 1. Per capita net availability of food grains in India (g/day)

Inadequate or lack of purchasing power among the poor is the main cause of food insecurity in rural India. As reported by Rajendra Prasad (2003), the per capita consumption of most food items in rural India is far below the recommended dietary allowances (Table 2). Though the per capita intake of cereals in all regions, and sugar and milk consumption in North and Western regions is closer to or above the standard requirements, the consumption of all other food items throughout the country is woefully lower than their respective dietary requirements as per ICMR (Indian Council of Medical Research) norms. A general low intake of pulses, vegetables, fruits, fats and oils, eggs, meat and fish is responsible for widespread occurrence of protein energy malnutrition (PEM) and chronic energy deficiency (CED). It was reported that 23 to 70 percent of the rural population in different parts of the country is suffering from protein energy malnutrition, while the chronic energy deficiency affected 17 to 54 percent of people (Table 3). Prevalence of poverty and low and fluctuating income levels also limit the access to diversified diet and thus adversely affect balanced diet. The vegetable products account for a lion share in the intake of all dietary constituents. A comparison of share of vegetable products and animal products in meeting total dietary energy, protein and fat in India, USA and the World as a whole makes this point clear. In India, vegetable products provide 93 percent dietary energy, 84 percent protein and 73 percent fat, while animal products supply the remaining small portion, i.e., 7 percent, 16 percent and 27 percent of energy, protein and fat, respectively. On the contrary, in a developed country like USA, the animal products account for 30 percent, 64 percent and 511 percent share in meeting dietary energy, protein and fat supply, respectively. Child malnutrition rates in India are still very high. According to the UNDP, 53 percent of children under five in India were under-weight during the period 1990-97, the highest rate from any of the 174 developing countries listed.

Table 2. Per capita food consumption in rural India (g/day)

Table 3. Extent of PEM and CED in rural India

2. Threats to future food security and livelihood in India

2.1 Growing population

In India, unabated growth in population has been and will continue to be the single most factors that have the potential to negate all the progress made in agricultural production. India’s population grew at an annual growth rate of around 2 percent in 1970s, 1980s and 1990s to reach 1 027 million in 2001 and is estimated to increase further to 1 262 and 1 542 million by the year 2011 and 2021, respectively (Sekhon, 1997). Growing population means mounting more pressure on natural resources to meet increased food demand. According to a conservative estimate (Kumar, 1998), the food grain demand in India for the years 2010 and 2020 is projected to be 246 and 294 mt, respectively (Table 4). This means that India’s food grain production has to increase from 212 mt (highest production ever achieved in 2001-02) to 246 mt in 2010 and then to 294 mt in 2020. It is by all means a daunting task and the ability to accomplish this task determines the future food security of the country.

Table 4. Current production and future demands of food grains in India

2.2 Declining land to man ratio and size of farm holdings

With continued rise in population, the arable land to man ratio has decreased from 0.5 ha (1951) to 0.14 ha at present and is expected to decline further to 0.08 ha by year 2020. The average number of land holdings has also increased simultaneously from 77 million (1976-77) to over 115 million at present due to population growth and the law of inheritance of land property. The average size of operational farm holding is only 1.57 ha. Further, about 78 percent of the 115 million farm holders in the country come under small and marginal category with the size of farm being less than 2 ha. The small size and scattered nature of the holdings will adversely affect the farm efficiency and will result in high cost of production. This in turn will result in low productivity and thus reduced agricultural sustainability and food security.

2.3 Decreasing total factor productivity

The total factor productivity (TFP) is used as an important measure to evaluate the performance of a production system and sustainability of its growth pattern. As stated earlier, adoption of green revolution technology led to a phenomenal growth in agricultural production during 1970s and 1980s. But of late, there are signs of fatigue in the agricultural growth process. In spite of continued growth of inputs, there has been no matching growth in agricultural production during 1990s, indicating a decrease in TEP. The declining trends of annual growth rate of productivity in respect of all major crops (Table 5) are also suggestive of decreasing TFP in Indian agriculture. In fact, all the crops except wheat registered a negative annual growth rate in their productivity during the recent past (2000-01 to 2002-03). If this alarming trend is allowed to continue, it will spell doom on the country’s future food security prospects. Reasons for decreasing the total factor productivity are:
(1) High nutrient turn over in soil-plant system coupled with low and imbalanced fertilizer use,
(2) Emerging deficiencies of micro and secondary nutrients (S, Zn, B, Fe, Mn, etc.), (3) Soil degradation due to acidification, aluminum toxicity, soil salinization and alkalization, soil erosion, (4) Wide nutrient gap between nutrient demand and supply, and (5) Consequent deterioration in soil physical, biological and chemical quality and low fertilizer use efficiency.

Table 5. Productivity growth rate of important crops in India

3. Reasons for declining total factor productivity

3.1 Wide nutrient gap between nutrient demand and supply

The growth in fertilizer consumption slowed down during 1990’s and there is stagnation in consumption during the last 4-5 years. After achieving a record consumption level of 18.1 mt of NPK in 1999-2000, the total NPK consumption is hovering around 16-17 mt during the last 3 years (2001-04). At the present level of crop production, there exists a negative balance of 10 mt between nutrient (NPK) demand by crops and supply of nutrient through application of fertilizer annually (Figure 1). The stagnant situation in fertilizer consumption and higher negative nutrient balance are posing a threat to soil quality and sustainable agriculture. It is now imperative to review the reasons for the stagnant trend in fertilizer consumption and take remedial action to alter this trend. The stagnant trend in fertilizer consumption despite slow increase in maximum retail price of fertilizers reveals that besides pricing, there are various other reasons which affect the fertilizer consumption. Weather cannot be solely blamed for the stagnant situation as the performance of southwest monsoon had been normal in the last few years (except 2000-03). The total NPK consumption did not exceed 17 mt during the year-2003-04, in spite of having good southwest monsoon rainfall. Deteriorating soil quality and the emerging deficiencies in secondary and micronutrients aside from major nutrients appear to be one of the major factors in the stagnation of fertilizer consumption. A cereal production of 5-10 t/ha/year in rice-wheat rotation, which is the backbone of India’s food security removes 380-760 kg N-P₂O₅-K₂O per hectare per year. Farmers generally apply 50 percent to 80 percent of this amount. Thus there is a gradual depletion of the inherent soil fertility.

Figure 1. Projected food grain production in relation to nutrient (N-P₂O₅-K₂O) consumption, removal and gap

3.2 Soil nutrient balances under intensive cropping systems

There are hardly any farm-level exercises which have been or are being conducted to monitor nutrient balances in intensively cropped areas. It is generally accepted that soils are being mined and that their nutrient capitals being continuously depleted throughout intensively cultivated areas. No quantitative or semi-quantitative estimates, however, are available on nutrient recycling or balances based on various input-output components at the farm level. This is an area where some insights from a few well-defined benchmark farms (not research stations) will be extremely valuable in developing sustainable systems, not only for site-specific adoption, but also for adoption to similar environments.

The fate of soil nutrient capital and balance in the two most important cropping systems of Uttar Pradesh is illustrated below (Table 6). These computations are primarily illustrative and based on several assumptions, due to the present inadequate database. The initial soil nutrient capital is taken to reflect the soil’s low status in nitrogen, medium in phosphorus, and high in potassium for the plow layer. Fertilizer inputs for the sugarcane-wheat system are typical of the practice. The analysis shows that after one cycle of the sugarcane-wheat system, the initial soil nutrient capital decreased by 23 percent in the case of N, increased by 1.2 percent in the case of P but decreased by 104 percent in the case of K. The improvement in P status was attributed to its application to both the main crops and input of FYM and press mud, that less was removed from the crop than was added and the ability of P (unlike N) to accumulate in the soil. The large depletion in K was due to its very weak position in the fertilizer use pattern and crop removal exceeding the K input.

Table 6. Nutrient balance after a sugarcane-wheat system in western Uttar Pradesh (productivity 120 mt cane/ha/2 crops + 3 tonnes wheat grain/ha)

The apparent K balance of long-term fertilizer experiment under maize-wheat-cowpea during 27 years of cropping showed that mining of soil K occurred even under NPK and NPK + FYM treatments, i.e. application of 15 t FYM/ha along with recommended rates of NPK (Swarup, 2002). This shows that the selection of suitable components of INM should vary with cropping systems and nutrient requirement. Integration of crop residues, along with farmyard manure and fertilizers, may arrest the mining of K from soils where the production systems have higher K demand.

3.3 High nutrient turnover in soil-plant system coupled with low and imbalanced fertilizer use

Fertilizer consumption in India is grossly imbalanced since the beginning. It is tilted more towards N followed by P. Further the decontrol of the phosphatic and potassic fertilizers resulted in more than doubling the prices of phosphatic and potassic fertilizers. Thus, the already unbalanced consumption ratio of 6:2.4:1 (N:P₂O₅:K₂O) in 1990-91 has widened to 7:2.7:1 in 2000-01 as against favourable ratio of 4:2:1 implying there from that farmers started adding more nitrogen and proportionately less phosphatic and potassic fertilizers. Even today, the situation is grim as far as fertilizer application by farmers is concerned. In many areas the imbalanced fertilization is the root cause of poor crop yields and poor soil fertility status. Accordingly, agro-ecological regions 4, 9 14, 15 and 18 and cropping systems like rice-wheat, maize-wheat, rice-pulse, potato-wheat and sugarcane demands immediate attention to correct the imbalances in nutrient consumptions to prevent further deterioration of soil quality and to break the yield barriers. There is wide variation in the consumption ratios of fertilizers from region to region but in the absence of information on the extent of cultivated area and details of cropping patterns in each agro-ecological region, it is difficult to estimate the crop removal of each region (Table 7).

Table 7. Critical areas of imbalances in fertilizer consumption

3.4 Emerging deficiencies of secondary and micronutrient in soils

Intensive cropping systems are heavy feeders and are bound to heavily extract nutrients from the soil. Hence, nutrient deficiencies are inevitable unless steps are taken to restore fertility levels. Deficiencies of essential elements in Indian soils and crops started emerging during the 1950s after the initiation of the government of Independent India, a five-year plan to give a fillip to food production through intensification. As food production increased with time, the number of elements becoming deficient in soils and crops also increased (Figure 2). Unless corrective measures are taken immediately, the list of essential elements becoming deficient is bound to increase further. A classical example of the effect of imbalanced fertilizer use is the fertility decline in an intensive cropping for over 25 years that has been reported by Swarup and Ganeshamurthy (1998). When only N was applied the P and K status in soils at all the centers have gone down. When N & P were applied the soil K status declined more conspicuously in alluvial soils (Ludhiana), Terai soils (Pantnagar) and laterite soils (Bhubaneshwar). All secondary and micronutrients generally declined in all the soils.

Figure 2. Food grain production and emerging nutrient deficiencies in soils of the country due to intensive cropping (modified from source: Swarup and Ganeshamurthy, 1998)

Although not universal, deficiency of S has cropped up as serious obstacle in the sustainability of yields in cropping systems particularly if a sulphur responsive crop like rice, oil seed or pulse crop is involved. The extent of S problems depends more on input of S through irrigation and atmosphere, the information from which is completely lacking. The results of long-term experiments (Table 8) show that response was very little in certain crops like wheat and jute and very conspicuous in certain other crops like rice and soybean.

Table 8. Mean grain yield response (kg/ha) of rice and wheat at Pantnagar

Micronutrient deficiencies in soils are also emerging as yield limiting factors. Analysis of 1.5 lakh soil samples from different regions of the country indicated that about 47 percent of soils were deficient in available Zn, 20 percent of samples were deficient in available B, 18 percent of samples were deficient in Mo, 12 percent of samples were deficient in available Fe and 5 percent of soil samples were found deficient in available Cu. Among the micronutrients, zinc deficiency is widely encountered followed by B, Mo and Fe, in that order. Field scale deficiency of Zn in crops is being increasingly reported. But suggestions that B and Mo as yield limiting factors are not convincing as trials that include these elements rarely generate conclusive evidence to support this hypothesis. Field scale Mo deficiencies and Mn as a factor of yield decline is not common. However, exception to this is in the rice-wheat system on sandy soils and reclaimed sodic soil. Continuous cropping of rice-wheat on these soils led to deficiency of Mn in wheat crop following leaching of reduced Mn from surface soils under rice culture. The productivity of wheat could be restored by soil and foliar applications of Mn ( Swarup and Ganeshamurthy, 1998).

3.5 Soil degradation

It has been stated that of the total 328.73 m ha geographical area, nearly 188 m ha of land in the country is potentially exposed to various degradation processes (Sehgal and Abrol, 1994). The land area subjected to degradation by way of soil displacement through erosion by water and wind is estimated at 148.9 and 13.5 m ha, respectively (nearly half of the area). About 13.8 m ha is under chemical deterioration due to loss of nutrients and organic matter, salinization and sodification. Soil acidification also rendered about 49 m ha of land degraded.

4. Integrated nutrient management strategies for sustainable food security and livelihood

Adequate plant nutrient supply holds the key to improving the food grain production and sustaining livelihood. Nutrient management practices have been developed, but in most of the cases farmers are not applying fertilizers at recommended rates. They feel fertilizers are very costly and not affordable and due there is a risk particularly under dry land conditions. Therefore, INM plays an important role which involves integrated use of organic manures, crop residues, green manures, biofertilizers etc. with inorganic fertilizers to supplement part of plant nutrients required by various cropping systems and thereby fulfilling the nutrient gap.

The basic concept underlying the principle of integrated nutrient management is to maintain or adjust plant nutrient supply to achieve a given level of crop production by optimizing the benefits from all possible sources of plant nutrients. The basic objectives of IPNS are to reduce the inorganic fertilizer requirement, to restore organic matter in soil, to enhance nutrient use efficiency and to maintain soil quality in terms of physical, chemical and biological properties. Bulky organic manures may not be able to supply adequate amount of nutrients, nevertheless their role becomes important in meeting the above objectives. Long-term studies being carried out under all Indian Coordinated Research Project have indicated that it is possible to substitute a part of fertilizer N needs of kharif crop by FYM without any adverse effect on the total productivity of the system in major cropping systems such as rice-rice, rice-wheat, maize-wheat, sorghum-wheat, pearl millet-wheat, maize-wheat and rice-maize. Sustainable yield index (SYI) of maize-wheat cropping system after 27 years at Ranchi was the highest with integrated use of 100 percent NPK and FYM (Table 9). Organic manures alone cannot supply sufficient P for optimum crop growth because of limited availability and low P concentration. The organic manures are known to decrease P adsorption/fixation and enhance P availability in P-fixing soils. Organic anions formed during the decomposition of organic inputs can compete with P for the same sorption sites and thereby increase P availability in soil and improve utilization by crops. Reddy et al. (1999) observed higher apparent P recovery by soybean-wheat system on Vertisol with a combination of fertilizer P and manure. The INM strategies developed for different cropping systems all over the country are compiled and presented in the Table 10.

Table 9. Effect of INM on sustainable yield index (SYI) in maize-wheat system after 27 years at Ranchi

Table 10. IPNS strategies for major cropping systems

4.1 Recycling of crop residues and green manuring

Management of crop residues is either through of the following 3 methods; removal, burning or incorporation into soil. Burning is a minor practice in India. Sidhu and Beri (1989) reported that in situ recycling of crop residues in rice-wheat rotation reduced grain yield of rice and wheat. Therefore, most of the farmers recycle the crop residues not by choice but due to combine harvesting, burn the residue causing loss of precious organic matter, plant nutrients and environmental pollution. Experiments conducted in Punjab have shown that co-incorporation of green manure and crop residues of wheat and rice helped alleviate the adverse effects of unburned crop residues on crop yields (Table 11).

Table 11. Effects of incorporation of green manure (G.M.) and crop residue on grain yield of rice (t/ha)

4.2 Role of biofertilizers in INM under intensive systems

Several studies clearly indicate that among the different types of biofertilizers available at present, Rhizobium is relatively more effective and widely used. Considering an average N fixation rate of 25 kg N/ha per 500 g application of Rhizobium, it is expected that 1 tonne of Rhizobium inoculants will be equivalent to 50 tonnes of nitrogen. On the other hand, +Azotobacter, which is used in non-legume crops has given inconclusive results. Similarly, Blue Green Algae (BGA) and Azolla have been reported to be effective only in certain traditional rice growing areas in the country. Meanwhile if BGA applied at 10 kg/ha fixes 20 kg N/ha, then 1 tonne of BGA has an equivalent fertilizer value of 2 tonnes of nitrogen. The beneficial effect of the organisms like Azospirillum and Azotobacter in suppression of soil-borne pathogenic diseases of crops is yet to be established on a pilot scale. Another important role of biofertilizers is liberation of growth substances, which promote germination and plant growth. Against the total anticipated biofertilizers demand of 1 million tonne in the country, the current supply position is very low (<10 000 tonnes). There are several constraints to effectively utilize and popularize the use of biofertilizers. Some of these constraints are:

• Unlike mineral fertilizers, use of the biofertilizers is crop and location specific. A strain found ideal at one location may be ineffective at another location due to competition of native soil microbes, poor aeration, high temperature, soil moisture, acidity, salinity and alkalinity, presence of toxic elements etc;
• Low shelf life of the microorganisms;
• Unlike mineral fertilizers, biofertilizers need careful handling and storage;
• Lack of suitable carrier material, for restoration and longevity in actual field conditions.

In order to overcome the above-cited constraints and make biofertilizers an effective supplementary source of mineral fertilizers, these aspects need to be critically attended.

5. Constraints in use of organics complementary with mineral fertilizers

Convenience and advantages in use of fertilizers

Though fertilizers are costly inputs in agriculture, they are ‘concentrated’ source of plant nutrients which can be formulated or tailored before or just prior to field application as per needs of the crops and can be applied with minimum transport and labour and at right time. Fertilizer use is high in irrigated crops, commercial crops and in peri-urban areas where awareness is high. The farmers are aware of the need for high nutrient use in high production areas under irrigated condition.

5.1 Selective use of fertilizers and manures

Fertilizer use is high in rice, wheat, sugarcane and cotton. Organic manures wherever available are invariably used in some vegetable crops like potato, onion, chillies, spices like ginger and turmic, in cereals like rice, in commercial crops like sugarcane, cotton and fruit crop banana. Green manuring is very prominent in rice and sugarcane and farmyard manure is commonly applied in arid and semi-arid dry land areas where costly fertilizers are discouraged due to the risk associated with their use and also due to the need for water for irrigation/soil moisture for better utilization of the applied nutrients. Farmers are also aware of the need for organics in dry land agriculture where some sort of stability to production is ensured because of its possible role in soil structure improvement and moisture storage and supply. The farmers in India apply good amount of organic manure (FYM, compost, goat, poultry and pig manure) at some periodicity to regenerate the soil fertility after three to five years of cropping.

5.2 Agro-ecological differences

Organic manure use is high in arid and semi-arid zones where rainfall/irrigation water or soil moisture is a limitation.

5.3 Peri-urban/rural differences

Developed market encourages farmers to use fertilizers and produce more under intensive system of cropping. Even small farmers use more fertilizers inputs, however in peri-urban areas, there is also possibility for use of agro-industrial or urban municipal wastes along with fertilizers to augment soil fertility. Farmers’ in remote areas with poor infrastructure and without access to market but are aware of the benefits of fertilizer use locally available organic sources.

5.4 Single multiple enterprises

Farmers who have less number of cattle may have to depend solely or mainly on fertilizers whereas farmers who practice several occupations like cash and field crops, dairy or livestock, poultry, fisheries enterprise etc., have opportunities to use/recycle the wastes, manures preferentially and profitably without depending on costly purchased inputs.

5.5 Land tenancy

The farmers who take land on tenure basis try to harvest high yields using mineral fertilizers and irrigation to ensure rapid returns to cover the cost of renting the land and may ignore the use of organiz manures especially in cereal crop production.

5.6 Lack of organic materials

Unavailability of organic materials especially animal manure and crop residues is a primary constraint in many areas.

5.7 Competitive use of organic resources

A very important example of competitive use is the use of cow dung as fuel because of the shortage of fuel wood. Similarly, crop straws or stalks like that of castor, red gram, cotton are used as fuel. Crop residues are also very valuable animal feed. Sometimes poultry manure/droppings are mixed with other additives and used as fish or cattle feed.

5.8 High cost of organic manures

Cost of organic manures especially animal manures is high in peri-urban areas where these manures are preferentially used in ornamental gardens, lawns and home gardens in raising vegetable crops.

5.9 Transport

Because organic manures are bulky, it is not convenient to transport and to apply them in all crops in all seasons. So it is applied conveniently in sufficiently good amount in remunerative crops at 4-5 years interval especially in kharif crops.

5.10 Pests, diseases and weeds

Some believe that the organic manures may carry pests, pathogens and weed seeds and propagate them in the current or following crops.

6. Farming systems approach

Besides the above stated constraints, to make INM a reality, micro-watershed based agricultural diversification through farming systems approach, consisting of crop and animal husbandry, horticulture, bee keeping, pisci culture, etc. are needed to be adopted. In general terms, the goal of farming systems approach is to increase and stabilize farm production and farm income. Having diverse enterprises creates opportunities for recycling, so that pollution is minimized because a waste in one enterprise becomes an input for another. The risk minimization, employment generation and sustained/increased household income are the benefits associated with multi-enterprise farming systems. Appropriate and situation-specific farm diversification models need to be developed and diffused. Efforts are underway in different locations to develop farm diversification models involving judicious enterprise mix that may provide attractive income besides meeting household demands from a given piece of farmland. One such model put forth by Behera and Mahapatra (1999) suggests an optimum integration of farm enterprises for a small land holding of 1.25 ha for Bhubaneshwar conditions. In this particular model, land was allocated for different enterprises in proportion to their significance in household needs and demand in local market. It was shown that with the adoption of this diversification model, a net income of Rs.58 360/year was derived from 1.25 ha farm land (Table 12). This kind of model is worth emulating in parts of the country as well in our search for comprehensive food and nutritional security.

Table 12. A farm enterprise diversification model for 1.25 ha farmland at Bhubaneshwar and its economics

7. Current status of INM

Keeping the importance of organic resources in view, a lot of research has been done on integrated nutrient management during last two decades in natural resource management (NRM) institutions and state agricultural universities. This research has led to:

• Development of INM practices for major crops;
• Understanding the enhanced role of organic manures in increasing input use efficiency due to their favourable effect on physical, chemical and biological condition of the soil;
• Establishing the beneficial role of integrated use of organic manures in improving nutrient cycling in different production systems in various types of soils;
• Beneficial role of INM in improving soil chemical, physical and biological quality for sustainable crop production; and
• The work on INM has been compiled and published in the form of books/bulletins by several institutions.

8. Research gaps in INM

The research gaps include:

• Mismatching of INM practices developed at research stations with the farmers’ resources and their practices;
• INM recommendations for different crops are not based on soil testing and nutrient release behaviour of the manures;
• Nutrient balance/flow analysis vis-à-vis soil fertility management practices with special reference to INM at farm level needs to be worked out;
• Nutrient release characteristics of farm residues in relation to their quality to develop decision support systems;
• Biofertilizers were not included as component of INM in many cases; and
• Integrated Farming Systems (IFS) approach needs to be encouraged for sustaining livelihood in rural areas particularly for small and marginal farmers.

References

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