免耕和稻草还田对稻田土壤氮素转化强度的影响

Effect of No-tillage and Straw Manuring on Paddy Soil Nitrogen Transformation Strength

为了明确土壤氮素转化对免耕和稻草还田的响应,研究了不同耕作对土壤(0～5 cm、5～12 cm和12～20 cm土层)氮素转化强度和铵态氮含量的影响。结果表明,免耕显著提高0～5 cm土层土壤氨化强度和铵态氮含量,但对于5～12 cm和12～20 cm土层趋势则相反;各土层土壤硝化势、反硝化强度免耕明显低于常耕,表明免耕促进0～5 cm土层有机氮的氨化作用和降低5～20 cm土层有机氮的氨化及0～20 cm土层土壤硝化-反硝化损失。稻草还田对土壤氮素转化强度的影响因耕作而异,免耕下,稻草还田促进5～20 cm土层土壤氨化强度及各土层反硝化强度和铵态氮含量,对0～5 cm土层土壤氨化强度和各土层土壤硝化势影响不大;常耕下,稻草还田降低5～20 cm土层铵态氮含量和硝化势,提高各土层氨化强度和反硝化强度。因而,免耕结合稻草还田更有利于土壤氮素的释放、供应,但需注意防止反硝化损失。

To better understand effects of no-tillage and straw manuring on soil nitrogen transformation, a field experiment was carried out and nitrogen transformation strength and ammonium nitrogen （AN） were measured in rice growth stage at different soil layers （0 - 5 cm, 5 - 12 cm and 12 - 20 cm） obtained from four tillage patterns. Results showed that no-tillage caused an increase in ammonification intensity and the content of AN at 0 - 5 cm soil layer while it showed an opposite trend at 5 - 12 cm and 12 - 20 cm soil layers. The nitrification potential and denitrification intensity were lower in no-tillage than that in conventional tillage at all soil layers. Therefore, no-tillage would help improve soil organic N mineralization at 0 - 5 cm soil layer but not at 5 - 20 cm soil layer and decrease nitrification-denitrification losses at different soil layers. However, straw manuring changed the tillage effect on soil nitrogen transformation. Comparing with treatments without straw manuring, straw manuring caused an increase in ammonification intensity at 5 - 20 cm soil layer and AN and denitrification intensity at all soil layers, and no changes in ammonification intensity at 0 - 5 cm soil layer and in nitrification potential at all soil layers under no-tillage, while decreased AN and nitrification poten t ial at 5 - 20 cm soil layer and increased ammonification intensity and denitrification intensity at all soil layers under conventional tillage. Therefore, NT combined with straw manuring would be much better for stimulating soil N release, but need to be careful for preventing denitrifying loss.