Soil organic carbon pools and productivity in relation to nutrient management in a 20-year-old rice-berseem agroecosystem.

摘要

Labile fractions of soil organic C (SOC) can respond rapidly to changes in C supply and are considered to be important indicators of soil quality. An attempt is made in this paper to investigate into the dynamics of total organic C (Ctot), oxidisable organic C (Coc), very labile C (Cfrac 1), labile C (Cfrac 2), less labile C (Cfrac 3), non-labile C (Cfrac 4), microbial biomass C (Cmic), mineralizable C (Cmin) and particulate organic C (Cp) in relation to the system productivity of a 20-year-old rice (Oryza sativa L)-berseem (Trifolium alexandrium L) cropping system with different management strategies [no fertilization, only NPK and NPK+FYM (farmyard manure) applied in different seasons] in the hot humid, subtropics of India. Cultivation over the years caused a net decrease, while balanced fertilization with NPK maintained the SOC. About 62% of the C applied as FYM was stabilized into SOC. The passive pool (Cfrac 3+Cfrac 4) constituted about 55% of the Ctot. A larger proportion (63%) of applied C was stabilized in the passive pool of SOC. Of the analysed pools, Cfrac 1, Cmic, Cp and Cmin were influenced most by the treatments imposed and explained higher per cent variability in the yield of the crops.