[目标]氮素矿化是决定土壤供氮能力的重要生态过程,养分添加和水分在调节土壤的氮转化方面起着重要的作用.探讨施氮和土壤水分对黑麦草还田过程中土壤氮素矿化的影响有利于进一步优化红壤旱地作物生产的水肥管理.[方法]通过室内培养试验,研究了施氮量(0、60、120mg/kg)和土壤含水量(15％、30％、45％)对红壤旱地黑麦草还田过程中土壤净硝化量、氨化量和氮矿化量的影响.[结果]土壤含水量15％时,施氮有利于提高黑麦草还田初期土壤净硝化量,施氮量120 mg/kg抑制了黑麦草还田后期土壤硝化作用.在30％土壤含水量时,施氮量120 mg/kg明显抑制了黑麦草还田后期土壤硝化作用.土壤含水量45％抑制了黑麦草还田初期不同施氮水平下土壤净硝化量,但增加了黑麦草还田91d时土壤净硝化量,且施氮量60 mg/kg下的净硝化量显著高于120 mg/kg水平下的.土壤净氨化量在整个黑麦草还田过程中均为正值,且呈现多次升高-降低的往复动态变化.土壤净氨化量在三种土壤含水量下均表现为施氮条件下的显著高于不施氮处理.土壤含水量的增加有利于提高施氮量120 mg/kg下黑麦草还田初期土壤的氨化作用,但降低了黑麦草还田后期土壤净氨化量.相比不施氮,三个含水量条件下的施氮处理在黑麦草还田过程中的大部分阶段都显著增加了土壤净氮矿化量,土壤含水量30％条件下土壤净氮矿化量的变化最大.相比土壤含水量15％,30％含水量促进了黑麦草还田中期(13～57 d)土壤净氮矿化量的增加,45％含水量抑制了黑麦草还田后期(73～91 d)土壤净氮矿化量.[结论]红壤区旱地黑麦草还田时应合理施入化学氮肥(60 mg/kg),在黑麦草还田初期保持较高的土壤含水量(45％)能够抑制土壤的氮矿化作用,还田中后期适当降低土壤含水量(30％)有利于增加土壤氮素的矿化.%[Objectives] Nitrogen mineralization is an important ecological process that determines ability of soil nitrogen supply.Nutrient elements addition and soil water content play important roles in regulating soil nitrogen transformation.Effect of nitrogen application and soil water content on soil nitrogen mineralization under ryegrass returning is beneficial to further optimize the management of water and fertilizer in upland red soil.[Methods] A laboratory experiment was conducted to study the effects of nitrogen rates and soil water contents on the soil net nitrification,ammonification and nitrogen mineralization under ryegrass (Lolium perenne L.)retuning into red soil.[Results] The results showed that under the 15％ soil water content,the nitrogen application improved soil net nitrification during the early stage of ryegrass returning,while in the late stage of ryegrass returning,the 120 mg/kg nitrogen application inhibited the soil net nitrification.Under the soil water content 30％,the 120 mg/kg nitrogen application significantly inhibited soil nitrification during the late stage of ryegrass returning.The soil water content of 45％ inhibited the soil net nitrification at different nitrogen rates in the early stage of ryegrass returning,but increased the soil net nitrification at 91 d,meanwhile,the soil net nitrification under the nitrogen application of 60 mg/kg was significantly higher than that under 120 mg/kg.The soil net ammonium was positive in the whole process of ryegrass returning,and was in a dynamic change of rise-fall reciprocating.Under the three soil water contents,the soil net ammonium under the nitrogen application was significantly higher than that without nitrogen application.The increase of soil water content was beneficial to increase the soil ammoniation during the early stage of ryegrass returning under the 120 mg/kg nitrogen application,but decrease the soil net ammonia content during the later stage of ryegrass returning.Compared with soil net nitrogen mineralization without nitrogen application,it was increased with the nitrogen application under the three water contents during the most process of ryegrass returning.The 30％ soil water content had the greatest change of soil net nitrogen mineralization.Compared with the soil water content of 15％,the 30％ water content promoted soil net nitrogen mineralization during the middle stage of ryegrass returning (13-57 d),but the 45％ water content inhibited soil net nitrogen mineralization during the late stage ofryegrass returning (73-91 d).[Conclusions] Reasonable chemical nitrogen fertilizer (60 mg/kg) should be applied during the ryegrass returning into red upland soil.Keeping high soil water content could inhibit soil nitrogen mineralization at the early stage of ryegrass returning.Reducing soil water content (30％) could increase soil nitrogen mineralization at the middle and late stages ofryegrass returning.
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