在干旱荒漠绿洲区大田试验条件下，研究了不同种植年限（0，3，4，5，7，10 a）苜蓿地土壤脲酶、碱性磷酸酶、蔗糖酶、淀粉酶、纤维素酶及过氧化氢酶活性的季节性动态变化，旨在探讨种植不同年限苜蓿对土壤生物化学性状的影响，为粮草合理轮作周期的制订提供科学依据。结果表明：种植苜蓿与撂荒地相比，土壤酶活性得到不同程度的提高，且各年限间土壤酶活性差异显著。其中土壤脲酶、蔗糖酶及纤维素酶活性均随生长年限增加呈先增高后降低再增加的变化趋势，而淀粉酶、碱性磷酸酶及过氧化氢酶活性均随种植年限增加呈先升高后降低的变化趋势，种植苜蓿5a 土壤酶活性增加最明显，0～60 cm 土层依次较 CK 分别增加了80．56％、69．91％、46．75％、533．33％、110．71％、11．81％；土壤6种酶的活性均随着土层深度的增加而减小，在表层0～20 cm 土层，土壤酶活性最强。脲酶和淀粉酶活性在夏季最高，蔗糖酶、纤维素酶、过氧化氢酶及碱性磷酸酶活性均在春季达到最高。对6种酶之间的相关性进行分析，研究发现除蔗糖酶外，其余5种酶间呈显著或极显著相关。%A field experiment was conducted to study the seasonal variations of soil enzyme activities (urease,alka-line phosphatase,sucrase,amylase,cellulose and catalase)in alfalfa field with different growing years (0,3,4,5,7, and 10 years)in arid desert oasis,and the purpose was to provide a theoretical basis for cereal-forage rotation system. Results indicated that different cropping years for alfalfa had effect on the activities of soil enzyme.In comparison with fallow farmland,the activities of soil enzyme were increased in various cropping years.The activities of urease,sucrase, and cellulose increased,and then decreased,and then increased with the increase of cropping years,but the activities of amylse,alkaline phosphatase,and catalase increased and then decreased with the increase of cropping years,the activi-ties of soil enzyme was the highest in five-years alfalfa,and was increased by 80.56%,69.91%,46.75%,533.33%, 110.71%,and 11 .81% in 0 ~60 cm depth compared with the CK,respectively.The activities of soil enzyme de-creased significantly with the increase in soil depth,being mainly concentrating in the 0 ~20 cm depth.The activities of urease and amylase were the highest in the summer,the activities of sucrase,cellulase,catalase,and alkaline phos-phatase were the highest in the spring.In addition,there existed significant correlations among the five kinds of soil en-zymes except sucrase.
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