中文摘要：

在砂培条件下，设置改良3：1式麦棉套作试验，采用1／2 Hoagland-Aron营养液培养棉苗，溶液法收集根系分泌物。以中性去离子水为对照，将收集到的棉花根系分泌物与不同粒径的土壤混合培养15d后，测定棉花根系分泌物对不同粒径土壤速效养分（速效氮、速效钾、速效磷）含量和土壤酶活性的影响。同时在大田条件下，研究改良3：1式麦棉套作系统中套种行土壤养分、微生物数量和土壤酶活性的变化。结果表明：棉花根系分泌物促进了土壤中磷、钾向有效态的转化，土壤速效氮（硝态氮、铵态氮）含量下降，速效磷、钾的含量分别比对照提高了19．2％和34．0％，土壤酶活性比对照提高了12．2％。细菌和真菌的数量比对照高49．8％和52．9％，土壤蔗糖酶活性升高。

英文摘要：

In order to determine effect of cotton root exudates on soil active-action nutrition and microbe, an experiment which comprised of several similar parts was carried out in Key Laboratory of Crop Growth Regulation. Under sand culture condition, cotton and wheat seedlings were planted in the form of the improved 3 ： 1 wheat-cotton intercropping system. Two weeks later, after root was washed carefully by DI （de-ions）, twenty cotton seedlings was transplanted in plastic box （1 L） contained 400mL DI （pH = 7）, then transferred to outdoor from am 10 ： 00 to pm 3 ： 00 under sunshine for 3 days. The solution in plastic box was collected and filtrated, concentrated under vacuum at 35℃ considered as root exudates. The collected cotton root exudates with different particle radialis soil and cultured 15 days in a phytotron （temperature 25℃）. Using neutral DI （de-ions） water as CK＇, effects of cotton root exudates on soil quick-acting nutrients contents （quick-acting nitrogen, phosphorus and potassium） and soil enzyme activity was studied. At the same time, under field condition, changes of soil nutrition, microbe quantity and soil enzyme activity in the improved 3 ： 1 wheat-cotton intercropping system was studied, too. The results showed that： 1） Cotton root exudates promoted soil phosphorus and potassium to the conversion of quick-acting. The contents of quick-acting nitrogen （NH4^＋- N, NO3^--N） indicated descent, however, quick-acting phosphorus and potassium ascent, with putting cotton root exudates in soil. Soil enzyme activity increased in cotton root exudates soil. 2） The contents of quick-acting phosphorus and potassium, microorganism quantity and soil invertase activity ascended with cotton root exudates.