Evaluation of Nitrogen Stabilizers on Nitrogen Use Efficiency of Poultry Litter.

The Poultry industry is one of the major industries in the US. It produces more than 44 million tons of poultry litter (PL) annually. Animal wastes including PL contain significant amounts of plant macro and micronutrients making them a good source of fertilizers. One of the major issues that is discouraging the application of PL/ animal wastes to agricultural lands is the relatively low concentration of nitrogen (N) compared to inorganic fertilizers coupled with loss of significant portions of N and P, which contribute to non-point source pollution. Strategies to minimize N losses from field applied PL/animal wastes can significantly enhance its value as a fertilizer. A 3-year field study was conducted to evaluate the use of N-stabilizers N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiamide (DCD) to improve Nitrogen use efficiency (NUE) of PL by minimizing N losses through NH₃ volatilization and N₂O emissions in a cotton crop. Treatments in the first year of the study include PL @ 90 kg N ha^-1, PL @ 90 kg N + 2.02 kg NBPT ha^-1, and PL @ 90 kg N + 4.04 kg NBPT ha^-1. Treatments in the 2^nd and 3^rd year were control, PL @ 90 kg N ha^-1, PL @ 90 kg N + 0.22 kg NBPT+ 2.72 kg DCD ha^-1, and PL @ 90 kg N + 0.44 kg NBPT + 5.44 kg DCD ha^-1. In all the years, application of N stabilizers at higher rate decreased NH₃ volatilization by an average of 11% as compared to PL only treatment. The decrease in NH₃ volatilization could be attributed to gradual conversion uric acid to NH₃ due to suppression of urease enzyme activity by N-stabilizers. N-stabilizer application also decreased N loss through N₂O emissions. Cotton tissue N-content was higher by as much as 2.8% in the treatments that received N-stabilizers along with PL application. Cotton lint yields increased by 12.3, 6.4 and 5.6 % in the year one, two and three, respectively, when the N-stabilizers were applied at the higher rate. Application of N-stabilizers at lower rate only increased yield in the first year. Overall, 3-year data supports the use of N-stabilizers to enhance NUE of PL applied soils similar to inorganic N fertilizers. Interpretation of 3-year data supports, between the N-stabilizers, NBPT application without DCD at 1.0 kg ha^-1 could be the optimum rate for enhancing PL or other animal residues’ NUE. DCD benefits to enhance NUE may be not economical due to minor contribution of N₂O losses from PL applied soils.