棉 花 学 报 Cotton Science 2007，19(1)：18-22
Effects of Root Exudates on Available Soil Nutrition，Micro-organism Quantity of Bt Cotton in Wheat-cotton Intercropping System Abstract：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 (1L) 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.
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