Belowground fertilization is a prevalent strategy for considerable grain yield and N utilization. However, the optimal fertilization depth remains uncertain in paddies, especially for slow/controlled release fertilizers. This study aimed to clarify the effect of deep “controlled-release blended fertilizer” (CRBF) fertilization on rice (Oryza sativa L.) yield and N utilization. Two N-fertilizer types were selected (a) urea and (b) CRBF, both combined at three fertilization depths (a) 0 cm, (b) 5 cm, and (c) 10 cm. The results showed that the grain yield was significantly affected by fertilizer type and fertilization depth. The yield achieved from CRBF was 7.8% higher than that from the urea application. Deep fertilization could also increase the rice yield with the optimum achieved from the 5-cm depth fertilization (yield increased by 15.1% compared to that from the manual surface fertilization). Overall, the 5-cm depth CRBF fertilization achieved the highest yield among all treatments with 12.21 and 11.84 t ha^–1 for 2018 and 2019, respectively. The larger sink was the main reason for this performance. Additionally, the higher photosynthetic efficient population after earing was another principal driver to the higher yield from CRBF. Due to the higher N uptake, CRBF application increased both N partial factor productivity (PFP) and recovery efficiency (RE) (P < .05); fertilization depth also had a striking effect on PFP and RE (P < .05 or .01). The 5-cm depth fertilization of CRBF achieved the highest N utilization for both years. The results suggest that 5-cm depth fertilization combined with controlled-release fertilizer is a suitable strategy for higher rice yield and N utilization.

中文翻译：

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控释肥深度施肥提高稻谷产量和氮素利用率：最佳施肥深度

地下施肥是获得可观粮食产量和氮利用的普遍策略。然而，稻田的最佳施肥深度仍然不确定，特别是对于缓/控释肥料。本研究旨在阐明深层“控释混合肥”（CRBF）施肥对水稻（Oryza sativaL.) 产量和氮利用率。选择了两种氮肥类型 (a) 尿素和 (b) CRBF，两者都在三个施肥深度 (a) 0 cm、(b) 5 cm 和 (c) 10 cm 处结合。结果表明，施肥种类和施肥深度对粮食产量有显着影响。CRBF 的收率比尿素应用高 7.8%。深度施肥还可以提高水稻产量，5 cm 深度施肥达到最佳效果（与人工表面施肥相比，产量增加了 15.1%）。总体而言，5 cm 深度的 CRBF 施肥达到了所有处理中最高的产量，分别为 12.21 和 11.84 t ha ^-1分别为 2018 年和 2019 年。较大的水槽是这种性能的主要原因。此外，穗后光合效率较高的种群是 CRBF 高产的另一个主要驱动因素。由于较高的 N 吸收，CRBF 应用提高了 N 部分要素生产力 (PFP​​) 和回收效率 (RE) ( P  < .05)；施肥深度对 PFP 和 RE 也有显着影响（P  < .05 或 .01）。CRBF 的 5 cm 深度施肥达到了两年来最高的氮利用率。结果表明，5 cm 深度施肥结合控释肥是提高水稻产量和氮素利用的合适策略。