Effect Of The Composite Root Population In Wheat-Cotton Inter-Cropping System On Cotton Root Growth, Absorbability And Distribution Of Nitrogen Of Cotton Plant And Soil Micro Ecology

In the symbiotic period of wheat and cotton, the competition for photo of overground and for nutrition of underground lead to cotton seedling infirmness, late gemmation and lead to cotton late maturation, inferior. Elucidating the physiological mechanism and regulation principles for competition for nutrition of underground in the symbiotic period of wheat and cotton is of important significance for nutrition complementary and guiding cultural management in cotton-wheat double cropping system. Under condition of high yielded cotton-wheat double cropping system, effect of the composite root population of wheat-cotton double cropping system on cotton root growth, absorbability and distribution of nitrogen of cotton plant and soil micro-ecology was studied by setting 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). Lumai 15, xumai 26 and Meimian 33B were used in the experiment. The principal results were as follows:1 Effect of the composite root population of wheat-cotton double cropping system on cotton root growth, in the symbiotic period of wheat and cotton, because of the competition difference for nutrition and water of cotton roots in different composite root population of wheat-cotton double cropping system, the MDA content of cotton root of WCRM was the highest, and which of WCRN was higher than WCRR So there were difference of cotton root dry matter accumulation and R/S among WCRM, WCRN and WCRP. Cotton root vigor of WCRM was higher than WCRN and WCRR but the root dry matter weight and R/S of WCRM were the lowest. After wheat had been harvested, the cotton root growth condition of WCRM had been superior to WCRN and WCRP, the MDA content of WCRM descended variously incoordinately.2 Effect of composite root population of wheat-cotton inter-cropping system on absorbability and distribution of nitrogen of cotton plant. In wheat-cotton inter-cropping system, there were not only nitrogen competing of wheat from soil of cotton root region,but also nitrogen moving to cotton from wheat root region soil. 15N-labeled nitrogen absorbed by cotton root was mainly distributed to the aerial parts of cotton plant, and little distributed to root, 15N-Iabeled nitrogen quantum of WCRM was the most, WCRN was the second and WCRP was the least. In the symbiotic period of wheat and cotton, Ndff, i.e. nitrogen quantity from the 15N-labeled fertilizer, for WCRM were the highest, nitrogen fertilizer of WCRM was mainly coming from soil. In the primary flower period, wheat had been harvested and wheat straw had been placed underground, nitrogen fertilizer of WCRM was mainly coming from fertilizer. 15N-labeled nitrogen distributing to different organs of cotton plant were different. It also proved that 15N-labeled nitrogen was found largely in the generative organs of cotton plant in the primary flower period. Dry weight of cotton plant of WCRM was higher than WCRN and WCRP.3 Effect of the composite root population of wheat-cotton double cropping system on soil microorganism quality and soil nutrient content at the rhizosphere and non-rhizosphere soil of cotton in the symbiotic period of wheat and cotton. In the symbiotic period of wheat and cotton, soil bacteria number of WCRM at the rhizosphere and non-rhizophere soil of cotton was the highest, and which of WCRN was higher than WCRP. but fungi number and actinomyces of WCRM were the lowest. In a word, WCRM was in favor of increasing the microorganism number at the rhizosphere and non-rhizosphere soil of cotton, it was turn up in changing of soil microorganism activity in WCRM. Above-mentioned change also influenced the soil nutrient content, i.e. total nitrogen content and available phosphorus content and rapidly available poassium content, the soil nutrient content of WCRM at the rhizosphere soil of cotton...