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自 1 98 4年开始的长期不同轮作与施肥试验表明 :种植作物可提高土壤供氮能力 6.88%～ 36.58%,以种植苜蓿提高幅度最大 ,是裸地的 1 .37倍。长期施用氮肥、磷肥、有机肥及三者配施可提高土壤供氮能力 9.8%～ 1 33.98%,其中以施氮、磷及有机肥玉米连作提高幅度最大。不同轮作系统中土壤供氮能力 :粮草 3年轮作 >粮草 8年轮作 >粮豆 3年轮作 >粮饲豆 4年轮作 ;种植作物可有效增加土壤有机氮水平 ,提高剖面土壤供氮能力。施用有机肥可有效地增加深层土壤供氮潜力并在 1 0 0 cm处出现迅速减小的现象
Long-term different crop rotation and fertilization experiments since 1984 show that planting crops can increase the soil nitrogen supply capacity by 6.88% -36.58%, and the maximum increase by planting alfalfa is 1.37 times that of bare soil. Long-term application of nitrogen fertilizer, phosphate fertilizer, organic fertilizer and their combination could increase soil nitrogen supply by 9.8% -1 33.98%, of which nitrogen, phosphorus and organic manure increased continuously. Soil nitrogen supply capacity in different rotation systems was: 3-year rotation of forage grass> 8-year rotation of forage grass> 3-year rotation of grain beans> 4-year rotation of grain-fed beans; planting crops could effectively increase the level of soil organic nitrogen and increase the nitrogen-supplying capacity of soil profile. The application of organic fertilizer can effectively increase the potential for nitrogen supply in deep soil and rapidly decrease at 1 0 cm