Evaluation of chemical and biological indices for carbon and nitrogen mineralization of various organic matters used in tea garden

The objective of this study was to evaluate the performance of chemical and biological indices to predict carbon and net nitrogen mineralization from a range of organic amendments that differed in their total carbon and nitrogen and the carbon quality. Three decomposed materials i.e. vermi compost (VC), farm yard manure (FYM), poultry manure (PM) and four un-decomposed materials i.e. raw cow dung (RCD), fish meal (FM), tannery waste (TW) and mustard cake (MC) were used for the experiment. Carbon mineralization was determined using alkali traps. Aerobic nitrogen mineralization was estimated using incubation and leaching method, whereas, anaerobic N-mineralization was done under waterlogged condition at 40°C. It was observed that water soluble organic carbon (WSOC) had significant correlation with C-mineralization (r=0.885**) and net aerobic N-mineralization (r=0.805*). Linear regression analysis also exhibited that WSOC had a very high linear relation with C-mineralization (r²=0.7835) and net N-mineralization (r²=0.649). Biological parameter i.e. 7 days anaerobic N-mineralization (ANI7) at high temperature exhibited significant correlation with C-mineralization (r=0.960**) and net aerobic nitrogen mineralization (r=0.855*). Net N-mineralization (aerobic) when regressed against anaerobic nitrogen index i.e. ANI-7, ANI-14 and ANI-21, R² value of 0.733, 0.945 and 0.960 were found, respectively, indicating that anaerobic nitrogen mineralization index can be a useful tool for predicting nitrogen mineralizing capacity of various organic matters.