Abstract: A two-year splitting plot test was conducted in the Songnen degraded Leymus chinensis grassland by cutting roots and applying nitrogen. The results showed that T-shaped root cutting (Q40) significantly reduced soil bulk density compared to the strip-shaped cutting method (Q20). Under the condition of root cutting,nitrogen application significantly increased soil total nitrogen and organic matter. The yield of Q40N4 was 310.91+10.623 g·m^-2,which was significantly higher than that of the control and other treatments. The yield of Q40N2 was 208.10+14.326 g·m^-2. Correlation and canonical correspondence analysis (CCA) showed that the actual contribution of soil physical and chemical factors to grassland biomass was only 34.23%. Monte Carlo substitution test showed that this explanation was credible,and P was the main soil limiting factor significantly affecting the annual yield of grassland in the region. Therefore,it is suggested to increase the use of phosphate fertilizer and remove the long-term P limitation of grassland soil in this region to obtain higher grassland biomass.

Key words: Cutting root, Nitrogen application, Degraded Leymus chinensis grassland, Soil physical and chemical properties, Biomass

摘要： 通过切根施氮在松嫩退化羊草草地开展连续2年的二裂式裂区试验。结果表明，井字型切根（Q40）较条形切根方式（Q20）显著降低了土壤容重。切根条件下，施氮处理显著提高土壤全氮和有机质。在所有切根施氮组合中，组合Q40N4（井字型切根宽度40cm方式下施氮4 kg·亩^-1）产量为310.91±10.623 g·m^-2，显著高于对照及其他处理，其中Q40N2处理的产量最少，为208.10±14.326 g·m^-2。相关性分析和典范对应分析（CCA）表明，土壤理化因子对草地生物量的实际贡献仅为34.23%。经蒙特卡罗置换检验表明，这种解释是可信的，且磷（P）元素是显著影响该区域草地全年产量的主要土壤限制因子。因此，在提高该区域羊草草地生物量方面，建议加大对磷肥的使用量，解除该区域草地土壤存在的长期磷限制，以获得较高的草地生物量。

关键词: 切根, 施氮, 退化羊草草地, 土壤理化性质, 草地生物量