中文摘要：

采用田间试验与室内分析相结合的方法，研究了氮肥形态对小麦不同生育期土壤酶活性的影响。结果表明：脲酶、蛋白酶活性随小麦生育时期推进呈现出两个峰值，蔗糖酶先降后升再降，呈倒‘S’型曲线，脱氢酶在越冬、成熟期高，其它生育期低，曲线似‘U’型，过氧化氢酶活性在返青后呈急剧上升，拔节后缓降。0～20 cm酶活性普遍高于20～40 cm；施肥可以提高土壤酶活性，可使脲酶活性提高60．3％，蛋白酶活性平均提高36．0％，蔗糖酶活性平均提高36．7％，脱氢酶活性平均提高100％，过氧化氢酶平均提高33．8％；土壤酶活性变异系数的平均值大小顺序是：脲酶＞脱氢酶＞蛋白酶＞蔗糖酶＞过氧化氢酶；氮肥形态对小麦不同生育期5种土壤酶的影响各异，没有一定的规律性。

英文摘要：

A field experiment was carried out to study the effects of nitrogen （N）fertilizer forms on soil enzyme ac-tivities at different growth stages of wheat .The results showed,during the whole growing season of wheat,the activities of urease and protease presented a two-peak curve,while the activities of invertase,dehydrogenase and catalase demon-strated an inverted S-curve （i .e .,decreasing-rising-decreasing）,U-curve （i .e .,being high at overwintering and maturity stage but low at other stages）,and inverted L-curve （i .e .,being risen sharply after reviving stage but de-creased slowly after jointing stage）,respectively .The enzyme activities in 0~20 cm layer of soil were generally higher than those in 20~40 cm layer .N application significantly improved soil enzyme activities,in which the activities of ure-ase,protease,invertase,dehydrogenase and catalase were elevated by 60 .3%,36 .0%,36 .7%,100%and 33 .8%on average,respectively .The average values of coefficient of variation of soil enzyme activities were sequenced as：urease〉dehydrogenase 〉protease 〉invertase 〉catalase .The effects of N fertilizer forms to soil enzyme activities at differ-ent stages of wheat were different,but there was no definite regularity .