Modification of Nitrogen Mineralization Dynamics of Rendered Animal Materials for Enhanced Nitrogen use Efficiency

Rendered animal materials could be an efficient and sustainable resources to supplement the energy intensive chemical fertilizers. Meat and bone meal (MBM) is a byproduct of rendered industry and a balanced fertilization source. Regulations imposed on the MBM use in animal feed, instigates to search for the alternative use of these materials, that otherwise goes to landfill. Soil application of MBM as a fertilizer to supplement the inorganic fertilizer is one of the promising strategy for their sustainable use. However, rapid initial mineralization dynamics of MBM could leads to nutrient losses and potential environmental pollution, necessitating the modification of mineralization rates from MBM. Here, we tested the mineralization control potential of nitrification inhibitors (Neem and Karanja cake) in MBM for extending the soil availability of mineralized plant nutrient elements (N). The associated changes in soil chemical properties, microbial biomass, gross ammonification and nitrification, soil enzymatic activities were measured. MBM exhibited a faster mineralization rate with more than 35% N in the MBM released into the soil within first 5 days of incubation. Neem and karanja amendments lowered the nitrification rate from MBM by 40% with retention of higher NH4+ (~35%) and net mineralized N (~35%) in the soil. The decrease in the ammonium mono-oxide activity (key enzyme to regulate the nitrification) with neem and karanja amendments lowered the rate of NH4+ oxidation, as NH4+ oxidation is the rate limiting step in nitrification. Lower gross nitrification at 18 days after incubation (DAI) was also observed under neem and karanja amendments along with MBM as compared to control (MBM only). Neem, karnaja and MBM improved the soil protease, alkaline/acid phosphatase enzyme activity and microbial biomass in the soils, suggesting no negative effect of nitrification inhibitors on the microbial growth and functionality. Overall, neem and karanja amendments retained more net mineralized nitrogen in the soil upto 21 DAI