Rice nitrogen (N) uptake and yield formation depend on both applied N fertilizer and soil-derived N. In this study, we determined the effects of topsoil removal on the N uptake and yield formation of rice crop. Four rice varieties were grown in farmers’ fields in Wuxue County, Hubei Province, China in 2016–2018 under the treatments of topsoil removal (TR) and control (CK). The TR treatment was established by desurfacing soil at about half of the topsoil depth (11−15 cm). Experiments were conducted in three adjacent fields in the three years and 100 kg N ha⁻¹ was applied in all plots except for zero-N treatment in 2018. Averaged across years, N treatments, and varieties, topsoil removal reduced total N uptake by 27.8 %. The period from midtillering to panicle initiation had the highest daily N uptake from topsoil compared with other growing periods. During this growing period, the percentage of N uptake from topsoil to plant N uptake ranged from 54.2 to 62.4 % with an average value of 56.4 % across both zero-N and N-applied treatments. On average, topsoil removal reduced grain yield by 16.7 % and total dry biomass by 17.6 %. Among yield components, panicles m⁻² was mainly responsible for the yield reduction in TR. Furthermore, total dry biomass rather than harvest index explained the yield reduction in TR compared with CK. Our results suggest that topsoil provided substantial N to rice crop especially during the period from midtillering to panicle initiation for achieving higher grain yield through increased panicles m⁻² and biomass production.

水稻对氮（N）的吸收和产量形成都取决于施用的氮肥和土壤来源的氮。在这项研究中，我们确定了表土清除对水稻作物氮素吸收和产量形成的影响。在表土去除（TR）和对照（CK）的处理下，2016年至2018年，湖北省武穴县的农民在田间种植了四个水稻品种。TR处理是通过在表土深度（11-15厘米）的一半左右对土壤进行表面处理而建立的。三年中在三个相邻的领域和100 kg N ha ^-1中进行了实验除2018年的零氮处理外，所有地块均采用了氮肥。表土去除的多年平均数，氮处理和品种的平均数使总氮吸收减少了27.8％。与其他生长时期相比，从分t到穗萌动时期的表层土壤每日氮吸收量最高。在这个生长期中，从零土壤到植物的氮吸收量占植物吸收氮的百分比范围从54.2％到62.4％，在施用零氮和施氮的处理中平均值为56.4％。平均而言，去除表层土壤使谷物产量降低了16.7％，总干生物量降低了17.6％。在产量构成要素中，圆锥花序m ^-2主要是TR产量下降的原因。此外，总干生物量而不是收获指数解释了与CK相比TR的产量降低。我们的结果表明，表土为水稻作物提供了大量的氮，尤其是在分t到穗开始期间，以通过增加穗m ^-2和生物量生产实现更高的谷物产量。