研究不同施氮水平下沙质土壤油莎豆（Cyperus esculentus）土壤养分表观平衡及块茎产量，为沙质土壤油莎豆科学施氮提供理论依据。以油莎豆品种“中油莎1号”为研究对象，分别设置0 kg·hm^-2（N0）、75 kg·hm^-2（N1）、150 kg·hm^-2（N2）、225 kg·hm^-2（N3）4个施氮水平。分析4个施氮水平对油莎豆农艺性状、土壤表观养分平衡及块茎产量的影响。结果表明：随着施氮量增加，两地油莎豆茎蘖数、株高、单片叶面积等均有增加，但过高的施氮量会造成油莎豆地上部徒长，导致产量下降；施氮量为150 kg·hm^-2（N2），油莎豆最大根长、根体积等农艺性状最优，油莎豆整株干重及块茎产量均最高，块茎鲜产可达到9298.87~10336.06 kg·hm^-2；两地氮素表观盈余率在0 kg·hm^-2（N0）和75 kg·hm^-2（N1）水平下均为负值，150 kg·hm^-2（N2）和225 kg·hm^-2（N3）水平下均为正值，表明两地氮素均在N2水平即施氮量为150 kg·hm^-2时达到氮素平衡状态。冗余分析也表明油莎豆茎蘖数、最大根长、根体积、氮携出量是驱动油莎豆干物质及块茎产量形成的主要因素。因此在北方沙质土壤条件下，N素施入量为150 kg·hm^-2时，可促进油莎豆对养分的吸收、维持土壤表观养分平衡，有利于油莎豆良好的生长发育和产量的提高。

This study aimed to investigate the apparent soil nitrogen balance and tuber yield of Cyperus esculentus in sandy farmland under different levels of nitrogen application and provide a theoretical basis for increasing the yield of Cyperus esculentus in sandy farmland. Four nitrogen fertilizer treatments, 0 kg·hm^-2 (N0), 75 kg·hm^-2 (N1), 150 kg·hm^-2 (N2), and 225 kg·hm^-2 (N3), were applied to Cyperus esculentus in 2021 at the experimental site in Dengkou County, Bayannur City, Inner Mongolia, and Toketo County, Inner Mongolia Academy of Agricultural Sciences, Hohhot, China. The effects of the four different N application levels on agronomic traits, tuber yield, and clear soil nutrient balance of Cyperus esculentus were analyzed. The number of tillers, plant height, and single leaf area of C. esculentus increased alongside increasing N application, but excessive N application caused above-ground growth of C. esculentus, resulting in lower yield. At the application rate of 150 kg·hm^-2 (N2), Cyperus esculentus exhibited superior agronomic traits, including maximum root length and root volume, the highest whole plant dry weight and tuber yield, and a fresh tuber yield of 9298.87 kg·hm^-2. The apparent nitrogen surplus rates in the two locations were negative at the levels of 0 kg·hm^-2 (N0) and 75 kg·hm^-2 (N1) and positive at the levels of 150 kg·hm^-2 (N2) and 225 kg·hm^-2 (N3). This pattern indicates that nitrogen reached a balanced state at the N2 level in both locations, signifying an optimal nitrogen application rate of 150 kg·hm^-2. RDA analysis showed that tiller number, plant height, single leaf area, maximum root length, root volume, and nitrogen uptake were the main factors driving the formation of dry matter and tuber yield in C. esculentus. Therefore, in northern sandy soil conditions, the application of N at 150 kg·hm^-2 can promote the absorption of nutrients by Cyperus esculentus and maintain the apparent nutrient balance of soil, which is conducive to the growth, development, and yield formation of Cyperus esculentus.