Largely accessible organic wastes can be turned into valuable compost product for raising crops organically on one hand, and get them disposed off safely at the other end. Straight use of organic wastes has tribulations like transportation and handling, wider C:N ratio, high application rates, nutrient overloading, weed seeds, pathogens, and metal toxicities. Composting bestows a tactic for coping high volumes of organic wastes in environmentally sound and desirable manners. Composted materials are remarkably regarded for their ability to improve soil health and plant growth, and suppress pathogens and plant diseases. Currently several composting systems have become available; ranging from a crude and slow windrows method, to the most speedy and computer monitored in-vessel system. Scientific investigations of this biological cum chemical process have reached to molecular level. Value addition of compost through beneficial microorganisms, mineral materials and fertilisers is also being considered. The nature and composition of materials put into composting is imperative for its quality rationale. On the whole, principles and processes governing composting are not so straightforward that ordinary enterprises could develop efficient composting facilities for the treatment of organic wastes. In this scenario, accessibility of comprehensive information to the scientific community as well as environmental protection agencies is imperative. This review article brings together the current information necessary for effective composting of organic wastes from different origins with diversified characteristics under various situations. It also covers the schematic description of well known composting systems, and various factors controlling the process.

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-Composting provides an excellent way to manage the huge volume of organic waste and convert it into a useful soil amendment. The effectiveness of composted organic waste can be further improved by enriching and blending it with nutrients and biologically active substances. The resulting value-added composts can be used at substantially low rates such as a few hundred kg per ha compared with conventional use of organic wastes in tons per ha. This approach could have practical significance in reducing the use of chemical fertilizer for sustainable agriculture and the environment. L-tryptophan is a precursor of the growth hormone indole acetic acid and is known to stimulate plant growth at extremely low concentrations. Here, we studied the effect of composted fruit and vegetable wastes, enriched with N at 133 g kg −1 compost, with or without L-tryptophan at 10 mg kg −1 compost, on soil and maize crops. The enriched compost was applied at 300 kg ha −1 to a sandy clay loam soil either by mixing with the top 15-cm soil layer in pots or as a band placement along the maize plants grown in the field. The compost was applied alone and in combination with 40 or 80 kg ha −1 urea N and compared with a treatment containing 160 kg N ha −1 , a full dose of N fertilizer alone, while P and K fertilizers were applied in all the treatments. Our results show that application of the enriched compost to soil increased aggregate stability by up to 24.8% and water retention by up to 43.1% compared with untreated control. A gradual increase in the concentration of indole acetic acid in compost, ranging from 1.02 to 3.34 mg kg −1 , was observed when compost was treated with its precursor L-tryptophan. The results of pot and field experiments revealed that compost enriched with N and L-tryptophan in the presence of 80 kg N fertilizer significantly increased cob and grain yields, by up to 19.8 and 21.4%, respectively, compared with a full dose of N fertilizer. These findings suggest that enrichment of composted organic wastes with N and L-tryptophan can change them into a value-added organic product that could be used as a soil amendment at rates as low as 300 kg ha −1 to increase crop production on a sustainable basis.auxins / biologically active substances / maize / nitrogen / organic fertilizer / organic waste / recycling soil aggregate

Manipulation of organic wastes and their composts as a source of organic matter (OM) and nutrients is imperative for sustainable agriculture. Further, the fortification of composts with chemical fertilizer enhances agronomic effectiveness of both by reducing the amount of fertilizer and improving the quality of compost. The present study aimed to explore the potential of organic and chemical nutrient sources with their optimal application and integration for sustainable wheat production. Accordingly, waste fruits and vegetables were collected, dried, ground and processed in a composting vessel. During the enriched composting, waste material (300 kg) was fortified with 30 kg N, i.e. 25% of the standard rate (120 kg N ha−1) of N fertilizer. Treatments for both greenhouse and field experiments using wheat (Triticum aestivumL.) included: control (without any compost or N fertilizer), compost (non-enriched), fertilizer N 120 (120 kg N ha−1), nitrogen-enriched compost (NEC), NEC+N 30 (30 kg N ha−1) and NEC+N 60 (60 kg N ha−1). Application rate of composts (non-enriched or enriched) was 300 kg ha−1in the respective treatments. Phosphorus and potassium fertilizers were applied at 90 kg P2O5ha−1and 60 kg K2O ha−1, respectively in all treatments. The crop was grown to maturity, and data on wheat growth and yield attributes were recorded. Application of NEC significantly improved the growth, yield and N, P and K contents of wheat compared with compost and control treatments. The performance of NEC+N 60 was statistically similar to that of fertilizer N 120. Economic analysis also revealed the superiority of NEC+N 60 over other treatments in terms of net return and relative increase in income; however, the value/cost ratio was highest with NEC alone. For effective and economical use of N fertilizer, it is suggested to integrate N fertilizer at reduced rates with NEC. Through enriched compost, application rates can be decreased from tonnes to kilograms per hectare, and dependence on chemical fertilizer can be reduced to a certain extent. So the approach is farmer friendly as it lowers compost application rates, and is economically acceptable as it saves N fertilizer. It is also environmentally sustainable due the recycling of organic waste and possible reduction of N losses to the environment. Thus, the study has wide application in the global environment and fertilizer market.

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