Comparative Effectiveness of Value-added Manures on Crop Productivity, Soil Mineral Nitrogen and Soil Carbon Pools under Maize-Wheat Cropping System in an Inceptisol

The effect of three value-added manures viz., vermicompost, NADEP compost and FYM was evaluated for crop production and maintaining soil mineral N and organic C pools in an Inceptisol under a maize-wheat cropping system. Vermicompost was prepared from various farm wastes using Eisenia foetida and cattle dung (5%, w/w). NADEP compost was prepared using mixed crop residues like maize, oat, berseem, jowar, lobia and seasonal grasses and cattle dung (2%, w/w) in pit, while FYM was prepared by trench method using cattle dung. Data revealed that yield and N uptake by maize and wheat due to conjoint use of valueadded manures and chemical fertilizers increased significantly over application of value-added manures alone. Mineral N and microbial biomass N (MBN) in soil improved significantly with application of 100% NPK than plots receiving organic manures alone as well as integrated use of manures and 50% NPK. Plots amended with value-added manures maintained higher soil organic carbon (SOC) pools viz., Walkley Black C (WBC), KMnO4-oxidizable labile C (LBC), microbial biomass C (MBC) and mineralizable C (C_min) over control. The effect in improving SOC pools further enhanced in plots amended with conjoint use of valueadded manure (5 Mg ha⁻¹) and 50% NPK fertilizers than plots amended with value-added manure alone. Pearson's correlation matrix showed significant and positive relationships between yield, N uptake by crops with soil mineral N, MBN and pools of SOC. The results demonstrated that integrated use of valueadded manures along with 50% NPK fertilizers could maintain higher mineral N and SOC pools, which may be considered as a feasible and environment-friendly option for recycling various farm wastes including crop residues and cattle dung into a value-added product, thereby effecting a 50% saving on costly chemical fertilizers.