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Long-term effects of fertilisers and organic sources on soil organic carbon fractions under a rice–wheat system in the Indo-Gangetic Plains of north-west India
- Das, D., Dwivedi, B. S., Singh, V. K., Datta, S. P., Meena, M. C., Chakraborty, D., Bandyopadhyay, K. K., Kumar, R., Mishra, R. P.
- Soil research 2017 v.55 no.3 pp. 296-308
- NPK fertilizers, animal manures, crop yield, long term effects, microbial biomass, mung beans, soil depth, soil organic carbon, India, Indo-Gangetic Plain
- Decline in soil organic carbon (SOC) content is considered a key constraint for sustenance of rice–wheat system (RWS) productivity in the Indo-Gangetic Plain region. We, therefore, studied the effects of fertilisers and manures on SOC pools, and their relationships with crop yields after 18 years of continuous RWS. Total organic C increased significantly with the integrated use of fertilisers and organic sources (from 13 to 16.03gkg-1) compared with unfertilised control (11.5gkg-1) or sole fertiliser (NPKZn; 12.17gkg-1) treatment at 0–7.5cm soil depth. Averaged across soil depths, labile fractions like microbial biomass C (MBC) and permanganate-oxidisable C (PmOC) were generally higher in treatments that received farmyard manure (FYM), sulfitation pressmud (SPM) or green gram residue (GR) along with NPK fertiliser, ranging from 192 to 276mgkg-1 and from 0.60 to 0.75gkg-1 respectively compared with NPKZn and NPK+cereal residue (CR) treatments, in which MBC and PmOC ranged from 118 to 170mgkg-1 and from 0.43 to 0.57gkg-1 respectively. Oxidisable organic C fractions revealed that very labile C and labile C fractions were much larger in the NPK+FYM or NPK+GR+FYM treatments, whereas the less-labile C and non-labile C fractions were larger under control and NPK+CR treatments. On average, Walkley–Black C, PmOC and MBC contributed 29–46%, 4.7–6.6% and 1.16–2.40% towards TOC respectively. Integrated plant nutrient supply options, except NPK+CR, also produced sustainable high yields of RWS.