Study on the effectiveness and mechanism of a sustainable dual slow-release model to improve N utilization efficiency and reduce N pollution in black soil.

Long-term intensive cultivation has led to serious N loss and low N fertilizer utilization efficiency (NUE) in black soil areas. The lost N is not only a waste of resources but also a serious pollution threat to the environment, leading to the decline in water quality and food safety and the greenhouse effect. In the present study, a stable dual slow-release model, CPCS-Urea, was prepared by in situ polymerization using nitrapyrin, urea and melamine-formaldehyde resin as raw materials. The effect of the dual slow-release model was systematically evaluated using two consecutive years of field experiments. Five treatments were established in the field experiment: no N fertilizer (N0), urea (N180), 1 % CPEC-Urea, 0.5 % CPCS-Urea, and 1 % CPCS-Urea. The results showed that the new dual slow-release CPCS-Urea model outperformed both the use of urea and the traditional slow-release CPEC-Urea model in reducing N losses and improving NUE. The application of CPCS-Urea reduced nitrate (NO) leaching by 28.2 %-47.2 % and NO emissions by 36.5 %-42.4 % and increased NUE by 20.7 %-28.5 % compared to urea application. The CPCS-Urea model modulated the activity of ammonia-oxidizing bacteria (AOB) and dissimilatory nitrate reduction to ammonium (DNRA) bacteria in soil, showing a significant decrease in AOB activity and an increase in DNRA activity. This results in a lower soil NO-N yield and a 53.1 %-72.0 % increase in NH-N content, providing sufficient N for the entire growth and development cycle of maize. In short, the dual slow-release CPCS-Urea model has great application prospects for promoting agricultural development in black soil areas.