Optimization of Nitrogen and Phosphorous Release Rates from Rendered Animal Products Using Natural Amendments.

Organic fertilizers could be an efficient and sustainable resources to supplement the energy intensive and unsustainable chemical fertilizers. Meat and bone meal (MBM) is a low cost, easily available, fertilizer source that has a balanced availability of nitrogen (N) and phosphorous (P). The mineralization dynamics of N and P from MBM is less known, so are its effects on plant growth. Lab incubation and greenhouse studies were conducted to evaluate the N and P mineralization rates from MBM incorporated into organic and conventional agricultural soils, the associated changes microbial biomass indices, ammonification and nitrification potential, soil enzymes activities, and the physiology accompanying the utilization of MBM by Zea mays.

MBM was subjected to hexane extraction to remove the lipids, which also increased the material consistency and lowered the carbon to nitrogen ratio. The elemental N, P, K content of the hexane-extracted MBM was 8.3 ± 0.3 %, 11.4 ± 0.4 % and 1 ± 0.01 %, respectively. Across both soils MBM exhibited a faster mineralization rate with more than 40% nitrogen in the MBM released into the soil within first 16 days of incubation. Rapid mineralization resulted in significant increase in soil pH, partly due to the deamination reactions that occur during ammonification. The supplementation of MBM with elemental sulfur was instrumental in maintaining the soil pH. Ammonium dominated the form of mineral N in both soils after MBM application, with ammonium-to-nitrate ratio exceeding 25 across all rate of S application. The orthophosphate content of both the soils also increased ~4 folds at 14 days after the application of MBM, and P mineralization decreased with an increase in S addition in organic soil. Naturally occurring plant amendments that can regulate the ammonification and nitrification process will be tested to regulate the initial rapid rate of mineralization of MBM.