稻麦轮作条件下长期不同土壤管理对供氮能力的影响

通过种植了 25季的长期定位试验研究了稻麦轮作条件下不同土壤耕作方式和培肥制度对土壤供氮能力的影响。结果表明 ,不论免耕还是耕翻 ,0～5cm土壤的氮素释放均较持久 ,5～15cm土壤的氮素释放耕翻较免耕持久。休闲的 0～5cm土壤在免耕条件下其氮素矿化势和短期矿化氮量均远远高于耕翻 ,5～15cm和 15～30cm土壤在免耕和耕翻间则相差不大。施肥的3个处理 0～ 5cm土壤氮素矿化势和短期矿化氮量有免耕高于耕翻的趋势 ,而 5～ 15cm土层免耕明显低于耕翻 ,15～ 30cm土壤免耕与耕翻没有差异。有机肥与化肥配施的免耕与耕翻土壤中 25季作物吸氮量几乎无差异 ,不施肥和单施化肥处理的免耕土壤中作物吸氮量低于耕翻土壤。免耕条件下 ,有机肥配施化肥土壤的供氮能力仅低于休闲土壤 ,不施肥土壤最低 ;耕翻条件下 ,有机肥配施化肥土壤的供氮能力最高。各培肥处理间的差异主要表现在 0～ 5cm土层。

Long-term impact of different soil management on nitrogensupplying potential in rice-based cropping system

A long term experiment was conducted to investigate the impact of different tillage and fertilization on the N mineralization potential of soils in rice based cropping system. The results showed that the nitrogen release potential in both of tilled and no tilled soils at the depth of 0 to 5cm was relatively lasting. The nitrogen release potential of tilled soils at the depth of 5 to 15cm revealed greater than no tilled soils. Fallowed soils at the depth of 0 to 5cm had remarkable higher No and N mineralized in short period (N_m) in no tilled soils (NT) than tilled soils (CT). But no evident differences of No and N m in soils at the depth of 5 to 15cm and 15 to 30cm between these two tillage methods were found . There was a trend that No and N_m in soils of treatments CF (only chemical fertilizer),PM (pig manure +chemical fertilizer) and CS (crop straw+chemical fertilizer) were higher under NT than under CT. No and N_m in no tilled soils at the depth of 15 to 30cm were greater than tilled soils. While the No and N_m between no tilled and tilled soils at the depth of 15 to 30cm did not differ significantly. N uptake by 25 crops in PM and CS treatments under NT was almost the same as that under CT, but in CK (no fertilizer) and CF treatments N uptake for NT was less than for CT. Under no tillage system, No and N_m in soils with combined fertilization (PM and CS) kept higher than CF and CK treatments while CK treatment was the lowest one, however, under fallow condition, No and N_m in soils normally showed very high;under tilled system , No and N_m for PM and CS were the highest among the all fertilization treatments. These differences mainly existed in the soils of the depth of 0 to 5cm.