长期连作和秸秆还田对棉田土壤生物活性的影响

研究了新疆棉区棉花长期连作与秸秆还田对棉田土壤微生物量和土壤酶活性的影响.结果表明：棉田土壤生物活性受到作物连作障碍的负面效应和秸秆长期还田培肥地力的正面效应的双重影响.在短期内（5～10年），连作障碍明显，连作与秸秆还田5和10年的土壤微生物总量比种植1年降低36.54%和25.66%，细菌、放线菌数量下降较快，分别为种植1年的61.12%、70.16%和67.91%、145.79%，而真菌所占比例提高；土壤中脲酶、蔗糖酶活性分别比种植1年降低0.76%、2.52%和28.12%、11.44%，连作与秸秆还田5年的过氧化氢酶活性比种植1年降低9.21%.长期连作与秸秆还田条件下，土壤生物性状趋于好转，生物多样性指数增加，与短期（5年）相比，连作与秸秆还田15和20年的细菌、放线菌数量分别增加71.52%、61.03%和141.74%、240.83%，而真菌所占比例下降，土壤中过氧化氢酶、蔗糖酶活性增加.淀粉酶活性在短期内上升，连作与秸秆还田5和10年分别比种植1年增加11.38%和10.41%，连作与秸秆还田20年则降低31.34%.

Effects of long-term continuous cropping of cotton and returning cotton stalk into field on soil biological activities.

The study on the effects of long-term continuous cropping of cotton and returning cotton stalk into field on the quantities of soil microbes and the activities of soil urease, invertase, catalase and diastase showed that the soil biological activities in cotton field were negatively affected by continuous cropping of cotton, but positively affected by the returning of cotton stocks into filed. The obstacle of short-term (5-10 years) continuous cropping was more obvious. After 5 and 10 years continuous cropping and stalk returning, the total quantity of soil microbes was decreased by 36.54% and 25.66%, and the quantities of bacteria and actinomyces were decreased by 61.12% and 70.16%, and 67.91%, 145.89%, respectively, while the quantity of fungi was increased, compared with those after 1 year cropping. The activities of soil urease and invertase after 5 and 10 years continuous cropping and stalk returning were decreased by 0.76% and 2.52%, and 28.12% and 11.44%, respectively, and the soil catalase activity after 5 years continuous cropping and stalk returning was decreased by 9.21%, compared with those after 1 year cropping. Under long-term continuous cropping and stalk returning, soil biological properties improved, and soil biological diversity index increased. Compared with those after 5 years continuous cropping and stalk returning, the quantities of bacteria and actinomyces after 15 and 20 years continuous cropping and stalk returning were increased by 71.52% and 61.03%, and 141.74%, 240.83%, respectively, with the proportion of fungi declined and the activities of urase, catalase and invertase increased. Soil amylase activity after 5, 10, and 20 years continuous cropping and stalk returning was increased by 11.38%, 10.41%, and 31.34%, respectively, compared with those after 1 year cropping.