Integrated Nutrient Management: Concept and Components
Authors: Vinod Kumar Sharma, Chiranjeev Kumawat and Rajendra Kumar Yadav*
PhD. Scholar, Division of Soil Science and Agricultural chemistry, ICAR-IARI, New Delhi-110012
*Corresponding author: raj91yadav@gmail.com


Introduction:

Integrated nutrient management (INM) is not a new concept. It is an age-old practice when almost all the nutrient needs were met through organic sources to supply secondary and micronutrients besides primary nutrients. In scientific literature, a few terminology variants like integrated plant nutrient supply (IPNS) and integrated nutrient supply and management (INSAM) are also used to convey almost similar meaning as that of INM.

2. INM/IPNS Definitions

INM or IPNS has been defined by different researchers as follows: IPNS is defined as maintenance or adjustment of soil fertility and supply of plant nutrient to an optimum level for sustaining the desired crop productivity through optimization of benefit from all possible resources of plant nutrients in an integrated manner. IPNS is used to maintain or adjust soil fertility and plant nutrient supply to achieve a given level of crop production. This is done by optimizing the benefits from all possible sources of plant nutrients. The basic concept of INM is the maintenance and improvement of soil fertility through integrating various nutrient resources along with fertilizers for sustaining crop productivity on long-term basis.

The concept includes key areas like, maintenance/adjustment of soil fertility, optimum plant nutrient supply, sustaining desired level of productivity, optimization of benefits from all possible sources of nutrients and addressing environmental concerns. 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.

This concept of nutrient management assumed greater significance in recent years because of two reasons. First, the need for continued increase in agricultural production and productivity requires growing application of nutrients and the present level of fertiliser production in India is not enough to meet the entire plant nutrient requirement. The impending demand-supply gap of about 10 million tonnes of plant nutrients is likely to widen further in view of steep hike in the prices of P&K fertilisers and raw materials. Second, a large number of experiments on INM, particularly long-term experiments (LTEs) conducted in India or elsewhere reveal that neither the fertilisers nor the organic sources in isolation can achieve sustained production under intensive cropping. Even the so called balanced use of fertilisers will not be able to sustain high productivity due to emergence of secondary or micronutrient deficiencies over time. The interactive advantages of combining organic and inorganic sources of nutrients in INM have proved superior to the sole use of these sources (Ray et al., 1991)

3. Components of INM

Fertilisers, organic manures, legumes, crop residues, and bio-fertilisers are the main ingredients of INM.

3.1. Fertilisers

Fertilisers continued to be the most important ingredient of INM. The dependence on fertilisers has been increasing constantly because of the need to supply large amounts of nutrients in intensive cropping with high productivity. Nonetheless, fertiliser consumption is not only inadequate but also imbalanced.

The N:P2O5:K2O use ratio is quite wide whereas application of K, S and micronutrients is often ignored. Domestic fertilizer production is inadequate to meet the requirements and the situation is not likely to improve in the near future. On the other hand, constraints like global price hike of fertilisers and raw materials would not permit fertiliser import in large quantities leading to a big gap between fertiliser supply and consumption. While organics and biofertilisers are expected to bridge a part of this gap, efficient use of fertilisers in narrowing the nutrient supply gap also needs greater emphasis. Utilization of fertiliser nutrients by the crops vary from 30-50% in case of N, 15- 20% in case of P and less than 5% in case of micronutrients. Thus substantial amount of applied nutrients is lost through various pathways. Enhancing nutrient use efficiency should, therefore, be a prioritized area of research for restoration and improvement of soil health and minimising the cost of crop production.

3.2. Organic Manures

Organic manures like urban compost, FYM, crop residues, human excreta, city refuse, rural compost, sewage-sludge, pressmud and other agroindustrial wastes have large nutrient potential. Compost and FYM have traditionally been the important manures for maintaining soil fertility and ensuring yield stability. Other potential organic sources of nutrients such as non-edible oilcakes and wastes from food processing industry are also there. Moreover, there are several industrial by-products and municipal wastes with fair nutrient potential. However, these nutrient-carriers have not been properly evaluated to establish their fertiliser equivalents. There is need to integrate these sources depending on their availability in different crops and cropping systems. The industrial byproducts like spent-wash from distillery, molasses, pressmud, etc., from sugar industry and wastes from other food processing industries have good manorial value. Sulphitation pressmud (SPM) has a great potential to supply nutrients in addition to favourable effects on soil properties. During the last three decades, SPM has assumed great importance as a nutrient supplement in sugarcaneratoon- wheat and other intensive cropping systems of the sugarcane growing areas. Municipal solid wastes (MSW) and sewage-sludge are the other important nutrient sources available for integration with fertiliser inputs, though these have to be used with caution to avoid any potential threat of pathogens and heavy metal load. These nutrient sources are bulky in nature with low nutrient content and short in supply; hence, have lost their relative importance over time in crop production. However, cost of fertilisers and their limited supply made it necessary to search for alternative and renewable sources of plant nutrients leading to major interest in organic recycling. Less than 50% of the manurial potential of cattle dung is utilized at present, as large proportion is lost as fuel and droppings in non-agricultural areas. Out of the cattle dung and other farmyard wastes recycled lack to the soil as manure, substantial nutrients are lost due to faulty methods of manure preparation and its amount of application. Organic manures not only supply macro and micronutrients, but also help improving the physical, chemical and biological properties of the soils. These manures, besides supplying nutrients to the first crop, also leave substantial residual effect on succeeding crops in the system.

3.3. Legumes

Legumes have a long-standing history of being soil fertility restorers due to their ability to obtain N from the atmosphere in symbiosis with Rhizobia. Legumes could prove an important ingredient of INM when grown for grain or fodder in a cropping system, or when introduced for green manuring. Legumes grown as green manure, forage or grain crops improved the productivity of rice-wheat cropping system (RWCS) and rejuvenated soil fertility (Yadav et al., 2000).

3.4. Crop Residues

Crop residues have several competitive uses and may not be always available as an ingredient of INM, yet in the regions like North-West India where mechanical harvesting is practiced, a sizeable quantity of residues is left in the field, which can form a part of nutrient supply. There are large amounts of residues of other crops like, potato, sugarcane, vegetables, etc., which are practically wasted in most cases.Although cereal crop residues are valuable cattle-feed, these could be used to supplement the fertilisers wherever available in excess of the local needs.Disposal of rice straw in Trans- and Upper Gangetic Plains has emerged as a great problem. In these combine-harvested areas farmers opt to burn the residues in situ, losing precious nutrients on one hand and polluting environment on the other. Recycling of these residues back to fields helps to build stable organic matter in the soil, as also to sustain crop yield levels. Stubbles left in the field even in traditional harvesting methods range from 0.5 to 1.5 t/ha in case of different crops. When mechanical harvesting is done, this amount is much greater. Stubbles of coarse cereals such as sorghum, maize, pearl millet, etc., which are difficult to decompose are normally collected and burnt during land preparation causing significant loss of plant nutrients.

3.5. Biofertilisers

Biofertilisers are the materials containing living or latent cells of agriculturally beneficial microorganisms that play an important role in improving soil fertility and crop productivity due to their capability to fix atmospheric N, solublize/mobilize P and decompose farm waste resulting in the release of plant nutrients. The extent of benefit from these microorganisms depends on their number and efficiency which, however, is governed by a large number of soil and environmental factors. Bacterial cultures like Rhizobium, Azospirillium and Azotobacter have the ability to fix atmospheric N which in turn increase N supply to the crops. Bacterial cultures of Pseudomonas and Bacillus species and fungal culture of Aspergillus species help to convert insoluble P into plant usable forms and thus improve phosphate availability to the crops. Similarly, fungi like Vesicular Arbuscular Mycorrhizae (VAM) increase nutrient uptake particularly that of P due to increased contact of roots with larger soil volume. Rhizobium is the most well-known bacterial species that acts as the primary symbiotic fixer of N. These bacteria can infect the roots of leguminous plants, leading to the formation of lumps or nodules where the N fixation takes place. The bacterium’s enzyme system supplies a constant source of reduced N to the host plant and the plant furnishes nutrients and energy for the activities of the bacterium. The Rhizobium-legume association can fix up to 100-300 kg N/ha in one crop season and in certain situations leave substantial N for the following crop. This symbiosis can meet more than 80% of the N requirement of the legume crop.

The free-living N-fixer, Azotobacter imparts positive benefits to the crops through small increase in N input from BNF, development and branching of roots, production of plant growth hormones, enhancement in uptake of NO3-, NH4+, H2PO4-, K+ and Fe2+, improved water status of the plants, increased nitrate-reductase activity and production of antifungal compounds. In irrigated wheat, significant response to Azotobactor inoculation was recorded in large number of onfarm trials. Azotobacter has been found to contribute, in general, 20- 25 kg N/ha. Azospirillum colonises the root mass fixes N in loose association with plants. It has shown positive interaction with applied N in several field crops with an average response equivalent to 15-20 kg/ha of applied N. Several strains of P solubilizing bacteria and fungi have been isolated and inoculation with Psolubilizing microbial cultures is known to increase the dissolution of sparingly soluble P in the soil. Integrated use of the microbial cultures along with low-grade rock phosphate might add about 30-35 kg P2O5/ha. Soil inoculation with Pseudomonas striata, besides increasing grain yield of wheat, showed residual effect in succeeding maize on alluvial soil of Delhi. In a 3-year field study on sandy loam alluvial soils of Modipuram, however, PSM (Psolubilizing microbial culture containing Aspergillus awamori) inoculation of wheat seed did increase crop response to P and soil available P content over the noninoculated treatments, but the magnitude of increase in these parameters was generally too small to attain statistical significance. In recent years, K mobilising biofertilisers (KMB) and Zn solubilizing biofertilisers (ZnSB) have been introduced to augment the solubility of K and Zn in soil, respectively. The need of such bacteria to be evaluated extensively. Also, liquid biofertilizers have proved superior to the conventional (solid) carrier based ones. Blue-Green Algae (BGA) is another csimportant source of N to wetland rice. The most frequently mentioned estimates of N fixed by BGA inoculation are in the range of 20-30 kg N ha-1. Extensive field studies have shown that the incorporation of Azolla would allow N applications to be reduced by at least 30-40 kg/ha (Dwivedi et al., 2004).

The advantages of INM can be broadly enumerated as i) restoration and sustenance of soil fertility and crop productivity, ii) prevention of secondary and micronutrient deficiencies, iii) economizing in fertiliser use and improvement in nutrient useefficiency and iv) favourable effect on the physical, chemical and biological health of soils (Singhet al., 2012)

References:
1. Dwivedi, B.S., Singh, V.K. and Dwivedi, V., Application of phosphate rock, with or without Aspergillus awamori inoculation, to meet P demands of rice-wheat systems in the Indo-Gangetic plains of India. Aus. J.Exp. Ag. 44:1041-1050 (2004).
2. Roy, R.N. and Ange, A.L., In Integrated Plant Nutrition System (IPNS) and Sustainable Agriculture, pp. SV/1-1-SV/1-12, FAI, New Delhi (1991).
3. Singh, M., Dwivedi, B.S. and Datta, S.P., Integrated nutrient management for enhancing productivity, nutrient use efficiency and environmental quality. In: Soil Science in the Service of Nation, pp. 55-67, ISSS, New Delhi (2012).
4. Yadav, R.L., Singh, S.R., Prasad, K., Dwivedi, B.S., Batta, R.K., Singh, A.K., Patil, N.G. and Chaudhary, S.K., In Yadav JSP and Singh GB (eds), Natural Resource Management for Agricultural Production in India, pp. 775-870, ICMNR, New Delhi (2000).



About Author / Additional Info:
Ph.D Scholar, Division of Soil Science and Agricultural Chemistry, IARI New Delhi ,India