Application of controlled-release urea increases maize N uptake, environmental benefits and economic returns via optimizing temporal and spatial distributions of soil mineral N

The creation of controlled -release urea (CRU) is a potent substitute for conventional fertilizers in order to preserve the availability of nitrogen (N) in soil, prevent environmental pollution, and move toward green agriculture. The main objectives of this study were to assess the impacts of CRU's full application on maize production and to clarify the connection between the nutrient release pattern of CRU and maize nutrient uptake. In order to learn more about the effects of CRU application on maize yields, N uptake, mineral N (Nmin) dynamics, N balance in soil -crop systems, and economic returns, a series of field experiments were carried out in 2018-2020 in Dalian City, Liaoning Province, China. There were 4 different treatments in the experiments: no N fertilizer input (control, CK); application of common urea at 210 kg ha-1 (U), the ideal fertilization management level for the study site; application of polyurethane -coated urea at the same N input rate as U (PCU); and application of PCU at a 20% reduction in N input rate (0.8PCU). Our findings showed that using CRU (i.e., PCU and 0.8PCU) may considerably increase maize N absorption, maintain maize yields, and increase N use efficiency (NUE) compared to U. The grain yield showed considerable positive correlations with total N uptake in leaf in U and 0.8PCU, but negative correlations with that in PCU, indicating that PCU caused excessive maize absorption while 0.8PCU could achieve a better yield response to N supply. Besides, PCU was able to maintain N fertilizer in the soil profile 0-20 cm away from the fertilization point, and higher Nmin content was observed in the 0-20 cm soil layer at various growth stages, particularly at the middle and late growing stages, optimizing the temporal and spatial distributions of Nmin. Additionally, compared to that in U, the apparent N loss rate in PCU was reduced by 36.2%, and applying CRU (PCU and 0.8PCU) increased net profit by 8.5% to 15.2% with less labor and fertilization frequency. It was concluded that using CRU could be an effective N fertilizer management strategy to sustain maize production, improve NUE, and increase economic returns while minimizing environmental risks.