Evaluation of Controlled Release Urea on the Dynamics of Nitrate, Ammonium, and Its Nitrogen Release in Black Soils of Northeast China

Controlled release urea (CRU) is considered to enhance crop yields while alleviating negative environmental problems caused by the hazardous gas emissions that are associated with high concentrations of ammonium (NH(4)(+)) and nitrate (NO(3)(−)) in black soils. Short-term effects of sulfur-coated urea (SCU) and polyurethane-coated urea (PCU), compared with conventional urea, on NO(3)(−) and NH(4)(+) in black soils were studied through the buried bag experiment conducted in an artificial climate chamber. We also investigated nitrogen (N) release kinetics of CRU and correlations between the cumulative N release rate and concentrations of NO(3)(−) and NH(4)(+). CRU can reduce concentrations of NO(3)(−) and NH(4)(+), and PCU was more effective in maintaining lower soil NO(3)(−)/NH(4)(+) ratios than SCU and U. Parabolic equation could describe the kinetics of NO(3)(−) and NH(4)(+) treated with PCU. The Elovich equation could describe the kinetics of NO(3)(−) and NH(4)(+) treated with SCU. The binary linear regression model was established to predict N release from PCU because of significant correlations between the cumulative N release rate and concentrations of NO(3)(−) and NH(4)(+). These results provided a methodology and data support for characterizing and predicting the N release from PCU in black soils.