Effects of Controlled-Release Nitrogen Fertilizer on Rice Yield, Soil Nutrients, and Nitrogen Use Efficiency in Black Soil with Straw Return

This study used a 3-year field experiment to evaluate the effects of controlled-release nitrogen fertilizers (CRNFs) on rice yield, nitrogen (N) uptake, N recovery efficiency (NRE), N agronomic efficiency (NAE), N partial factor productivity (NPFP), and soil nutrients under straw-returning (SR) conditions in the black soil region of Northeast China. The results showed that CRNF combined with SR increased rice yield, NRE, NAE, and NPFP by 11.2%, 27.7%, 26.1%, and 22.3% respectively; the differences were significant when compared with common N fertilizer (CNF) combined with SR. In addition, CRNF increased soil organic matter (SOM), total N (TN), available N (AN), and other nutrients while reducing nitrate N (NO₃^--N) accumulation in the 30-60 cm soil layer. When the N application rate was reduced by 12%, rice yield still increased by 4.7%, and NRE, NAE, and NPFP increased by 17.2%, 32.9%, and 11.7% respectively; the differences were significant, and the content of soil nutrients has increased to varying degrees. These results indicate that a one-time basal application of controlled-release urea (CRU) mixed with bare urea (BU) at a 6:4 ratio can maintain stable yields, improve fertilization efficiency, reduce N fertilizer input, and lower environmental risks. Therefore, this approach represents an effective strategy for sustainable fertilization in rice-growing areas of Northeast China.