Effectiveness of a 10-year continuous reduction of controlled-release nitrogen fertilizer on production, nitrogen loss and utilization of double-cropping rice

Considerable literature has demonstrated the advantage of controlled-release nitrogen (CRN) fertilizer in improving crop productivity. However, few researches have explored the long-term impacts of using CRN fer-tilizers as alternative to common urea on production and N utilization in double-cropping paddy. To address this gap, our study utilized a database derived from a 10-year field experiment from 2013 to 2022. During early and late rice seasons, compared to common urea (early rice, 150 kg hm-2; late rice, 180 kg hm-2), CRN fertilizer (150 kg hm-2; 180 kg hm-2) input significantly increased yield by 7.4 %, and 11.7 %, as well as N use efficiency (NUE) from 23.0 % and 24.6 % to 33.0 % and 37.5 %, respectively. CRN application significantly reduced N losses, evidenced by decrease in runoff (23.1 % and 19.4 %), leaching (12.7 % and 12.1 %), ammonia volatil-ization (28.9 % and 30.2 %), and N2O emissions (10.4 % and 16.1 %). A reduction of 10 % in CRN fertilizer input maintained yield. Compared with normal amount, reducing 10, 20, and 30 % CRN input increased NUE by 7.0-7.6 %, 7.3-7.4 %, and 11.6-12.6 %; reduced runoff loss by 16.1-17.9 %, 27.9-30.7 %, and 35.0-37.2 %; decreased leaching loss by 7.6-12.8 %, 18.1-22.6 %, and 26.5-31.4 %; decreased ammonia volatilization by 9.9-12.3 %, 16.3-22.7 %, and 23.2-29.3 %, and decreased N2O loss by 7.8-13.3 %, 12.8-32.8 %, and 20.3-36.9 %, respectively. Soils with CRN input showed higher total and inorganic N contents than the soils with common urea, and the content increased in parallel with CRN fertilizer input. Soil N content and N runoff loss were significantly related to yield and N uptake, and N runoff and leaching losses were significantly related to NUE. These results support the sustainable use of CRN fertilizers as a viable alternative to common urea, indicating that application rate of 135 and 162 kg N hm-2 of early and late rice, respectively, maintain yield and enhance N utilization in double-season paddy of southern China.