黄土高原旱区长期不同轮作施肥对土壤供氮能力的影响

Effects of long term rotation and fertilization on N supply by soil in dryland area on loess plateau

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

The results of long term experiment started in 1984 show that:soil potential can be enhance effectively after continuous planting crops, and their elevation range from 6.88% to 36.58%; the highest increment of crops is purple alfalfa, and its soil potential is 1.37 multiples of bareness dispose. Long term fertilization (nitrogenous fertilizer、phosphorescence、organism fertilizer) can increase soil potential and organic fertilizer has the best effect. After long term fertilization, the N supply by soils were elevated from 9.8% to 133.98% and the best effect of crops is continuouslg planting maize, and its soil potential is 2.34 multiples of bareness dispose. Among long term rotation dispose, N supply by soils of the 3 year grain forage rotation is the greatest, and its amount add up to 156.4 kg/hm 2. The results also reflect that the rotation of grain pasture (sainfoin、purple alfalfa) has the better increment than rotation of grain legumine. Planting crop can raise the content of organic N and also N 0. Long term application of organic fertilizer can enhance N 0 better than other chemical fertilizers. The N supply by soils in soil profile decreased rapidly at 100 cm.