Organic Amendments Influence Soil Organic Carbon Pools and Rice–Wheat Productivity
2008
Majumder, Bidisha | Mandal, Biswapati | Bandyopadhyay, Premansukumar | Gangopadhyay, A. | Mani, P. K. | Kundu, A. L. | Mazumdar, D.
Soil organic C (SOC) pools under long-term management practices provide information on C sequestration pathways, soil quality maintenance, and crop productivity. Farmyard manure (FYM), paddy straw (PS), and green manure (GM) along with inorganic fertilizers were used in a 19-yr-old rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system in subtropical India to evaluate their impact on SOC stock, its different pools—total organic C (Cₜₒₜ); oxidizable organic C (Cₒc) and its four fractions of very labile (Cfᵣₐc₁), labile (Cfᵣₐc₂), less labile (Cfᵣₐc₃), and nonlabile C (Cfᵣₐc₄); microbial biomass C (Cₘᵢc); and mineralizable C (Cₘᵢₙ). Cropping with only N–P–K fertilization just maintained SOC content, while N–P–K plus organics increased SOC by 24.3% over the control, their relative efficacy being FYM > PS > GM. A minimum of 3.56 Mg C ha⁻¹ yr⁻¹ was required to be added as organic amendments to compensate for SOC loss from cropping. The passive (Cfᵣₐc₃ + Cfᵣₐc₄) pool and Cₘᵢₙ constituted about 39 and 11.5%, respectively, of Cₜₒₜ Organics contributed toward the passive pool in the order FYM > PS > GM. Most of the pools were significantly (P = 0.005) correlated with each other. Yield and sustainable yield index were strongly related with Cfᵣₐc₁, Cₒc, Cₘᵢc, and Cₘᵢₙ Results suggest Cfᵣₐc₁ as a useful indicator for assessing soil health, and balanced fertilization with FYM as suitable management for sustaining crop productivity of the rice–wheat system.
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