Abstract:

Field experiment method was used in this study, and five treatment methods were set up: a control group with no fertilizer application (CK), application of only phosphorus and potassium fertilizers (PK), application of conventional nitrogen, phosphorus, and potassium fertilizers (NPK), a combination of 80% controlled-release fertilizer and 20% conventional urea as base fertilizer (N2PK), and 80% controlled-release fertilizer as base fertilizer and 20% conventional urea as topdressing (N3PK). The study aimed to investigate the effects of controlled-release urea and conventional urea applied at different stages on rice yield and nitrogen fertilizer efficiency. The results showed that compared with the control group (CK) with no fertilizer, the PK treatment significantly promoted the growth of rice grain and straw, increasing yields by 25.7% and 11.8%, respectively. Grain and straw yields under nitrogen application treatments increased by 66.4% to 79.1% and 38.4% to 79.2%, respectively. Compared with NPK, the grain yields of N2PK and N3PK increased by 707 kg·hm^-2 and 562 kg·hm^-2, and straw yields increased by 29.5% and 18.4%, respectively. The yield-increasing effect of the N2PK treatment was more obvious. Although there were no significant differences in grain nitrogen content among the nitrogen treatments, the straw nitrogen content in N2PK and N3PK was significantly higher by 15.6% and 11.4%, respectively, compared with NPK. The nitrogen uptake by grains in N2PK increased significantly by 16.1%, and the nitrogen uptake by straw in N2PK and N3PK increased significantly by 49.7% and 31.8%, respectively. Nitrogen fertilizer application caused nitrogen accumulation in the soil, especially in the NPK treatment, which had a much higher nitrogen surplus than the controlled-release fertilizer treatments. The apparent utilization efficiency of N2PK and N3PK was higher by 21.9 and 12.5 percentage points, respectively, compared with NPK. Therefore, applying 80% nitrogen from controlled-release urea and 20% from conventional urea as base fertilizer is an optimal fertilization method, effectively improving rice yield.

Key words: rice, nitrogen fertilizer, controlled-release urea, efficiency, apparent balance