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1994~1995年对旱地玉米不同耕作系统土壤有机质、氮和酶进行了研究.结果表明,在6年的试验地上,免耕覆盖比常规耕作0~5CM土壤有机质平均高0.55个百分点,土壤PH值低0.19,硝态氮玉米田低30.35％,休闲田高30.37％,铵态氮玉米田0~20CM土层低58.3％,休闲田低5.57％,水解氮玉米田0~20CM,低4.97％,休闲田差别不大.20~50CM硝态氮、铵态氮和水解氮免耕覆盖与常规耕作之间差异不大.秋耕覆盖和秋耕秸秆还田是调控土壤供氮强度的两条主要措施.“,”A study was conducted under four environmental conditions during 1994 and 1995 in arid corn field to determine the effects of four tillage systems on soil organic matter,nitrogen and enzyme.The experiment was conducted using no?tillage with whold stalk mulch,mulch with whole stalk after full plow,conventional tillage and plough under the stalk after the harvest.Results indicated that:Compared with coventional tillage,soil organic matter increased by 0.55 percent at 0～5cm depth;pH decreased by 0.16,at 0～20cm...