Effect of the composite root population of wheat-cotton double cropping system on soil enzyme activity and soil nutrient content at the cotton rhizosphere and non-rhizosphere zones

صينى. 在麦棉两熟双高产条件下，设置麦棉自然根系（根系和肥水均可相互通过）、麦棉纱网隔根（肥水可相互通过，根系不能相互通过）和麦棉塑膜隔根（根系和肥水均不能相互通过）3种套种复合根系群体，研究麦棉两熟复合根系对棉花根际和非根际土壤酶活性和土壤养分的影响。结果表明，在麦棉共生期，与麦棉塑膜隔根相比，麦棉自然根系和纱网隔根复合群体中棉花根际非根际土壤脲酶、蔗糖酶和蛋白酶的活性均有所提高，其中以麦棉纱网隔根处理的土壤酶活性最高。同时，麦棉自然根系复合群体中棉花根际非根际土壤的养分含量降低，纱网隔根处理减缓了小麦根系对棉花根系营养的竞争，同时又可能是小麦根系分泌物的作用使其养分含量最高。到棉花盛蕾期，小麦已收获，麦棉复合群体根际和非根际土壤酶活性和土壤养分状况均得到不同程度改善，其中以麦棉自然根系复合群体的改善程度最大,其土壤脲酶和蔗糖酶的活性达到最高，土壤有机质和全氮含量超过塑膜隔根，但仍低于纱网隔根。麦棉套作地下部不仅存在小麦对棉花营养竞争的不利一面，同时还存在小麦根系促进棉花根际非根际土壤酶活性和土壤养分含量提高的有利一面，且此效应将持续影响套作棉花一生。

إنجليزي. Under the conditions of high yielding cotton-wheat double cropping system, the effect of the composite root population of wheat-cotton double cropping system on soil enzyme activity and soil nutrient content at cotton rhizosphere and non-rhizosphere zones was studied in 3 treatments, i.e. wheat-cotton double cropping system in which the roots of wheat and cotton mixed naturally (WCRM), wheat-cotton double cropping system in which the roots of wheat and cotton separated with nylon net (WCRN),and wheat-cotton double cropping system in which the roots of wheat and cotton separated with plastic film(WCRP). The results showed that: in the symbiotic period of wheat and cotton, compared with WCRP, the activity of urease, invertase and protease at cotton rhizosphere and non-rhizosphere soil increased in WCRM and WCRN, and the soil enzyme activity in WCRN was the highest one. The soil nutrient content at cotton rhizosphere and non-rhizosphere zones reduced in WCRM, and the soil nutrient content in WCRN was the highest one as a result of yarn net slowed down the nutrient competition of wheat root to cotton root and secretion from wheat root’s enhancement at the same time. In full-bud stage, wheat had been harvested, the soil enzyme activity and soil nutrient content at cotton rhizosphere and non-rhizosphere zones improved in different degrees in the composite root population, and WCRM improved the most, it’s urease and invertase activity was the highest, and the soil organic matter content and total nitrogen content were higher than WCRP, but lower than WCRN. In wheat-cotton double cropping system, there were not only disadvantage nutrition competition between wheat and cotton at underground part, but also advantage part in which the soil enzyme activity and soil nutrient content at cotton rhizosphere and non-rhizosphere zones improved.