Evaluating the impact of an organic nitrification inhibitor on nitrogen availability and its influence on microbial population in paddy soil

An incubation study was conducted to estimate the potential inhibition rates of nitrification using phytonim-coated fertilizers like urea and ammonium sulfate (AS) at different concentrations viz., 100 % and 65 % of the recommended dosage (RD) and additionally ammonifying bacteria (AB) was added with urea as one of the treatments. Samples were taken at 13 different intervals in a 45-day incubation experiment. Applying phytonim-coated fertilizers delayed the nitrification process for 35 days, improving the soils' available N. Ammonia oxidation and nitrite oxidation rates were reduced by 14 % and 35 % in phytonim-coated urea, 11 % and 23 % in phytonim-coated urea + AB and 24 % and 45 % in phytonim-coated AS, respectively over uncoated fertilizers. Nitrate reductase activity was reduced by 17 %, 16 % and 21 % in phytonim-coated fertilizers like urea, AS and urea + AB compared to uncoated fertilizers. Soil urease activity was inhibited in phytonim-coated urea (100 % RD and 65 % RD) of 9.6 % and 7.4 %, respectively, whereas 5.7 % and 6.7 % increased urease activity were observed in phytonim-coated urea + AB (100 % RD) and coated urea + AB (65 % RD). Increased soil dehydrogenase activity and FDA hydrolysis of 20 % and 15 % were observed in phytonim-coated urea, 15 % and 18 % in phytonim-coated urea + AB (100 % RD) and 17 % and 16 % in phytonim-coated AS over uncoated fertilizers. Results show that phytonim-coated AS (100 % RD) (T8) has inhibited nitrification most, followed by phytonim-coated urea (100 % RD) (T4) during the incubation period. This study concludes that applying organic nitrification inhibitors inhibited the nitrification and denitrification rates, affected the urea hydrolysis and positively affected the microbial population.