Regulating the nutrient release rates from proteinaceous agricultural byproducts using organic amendments and its effect on soil chemical and microbiological properties

Meat and bone meal (MBM) is a byproduct of the rendering industry and is considered an excellent potential organic fertilizer due to its balanced availability of nutrients. However, rapid nutrient mineralization of the MBM that is less synchronized with crop demand, could lead to significant nutrient losses, necessitating measures to modify the mineralization rates of MBM. Here we tested the influence of two natural nitrification inhibitors (NIs; neem cake and karanja cake) on the mineralization of carbon (C), nitrogen (N), and phosphorus (P) from MBM, the associated soil potential enzymatic activity, microbial abundance and broad composition and the influence of these process on plant growth. MBM mineralized quickly, with 35% mineralization of the applied N within the first 5 days of incubation. NIs reduced nitrification rate of MBM by ~ 40% and increased the retention of NH4+ (~ 35%) in soil compared with MBM only. Soil CO2 respiration, potential enzymatic activity and microbial abundance were similar in the MBM with and without NIs, suggesting a low negative effect of NIs on the microbial growth and functionality. MBM exhibits a slow P mineralization rate, with an increase in soil available P was observed only at later sampling points (36 days after incubation) with solubilization of a fraction of Ca-P. P mineralization rates were similar between the MBM with and without NIs. MBM with and without NIs was equally effective in maintaining the plant growth and biomass, which were similar to inorganic fertilizers. Our study suggests that MBM blended with NIs could increase the crop nutrient use efficiency via lowering N losses, while improving soil microbiological health.