Comparative Study On The Soil Fertility And Economic Benefits Under Multiple-cropping Systems In A Hilly-dry Land In Southwest China

From2007to2010year, using field experiment randomized trial design, the experiment respectively made the study from the two aspects, soil fertility and economic benefits of different cropping systems under location condition: wheat/maize/soybean(A1),wheat/maize/sweetpotato(A2),wheat/sorghum/soybean(A3), potato/maize/soybean(A4),wheat/maize-fallowland(A5),wheat-fallowland/soybean(A6), fallow land(A7), The results showed as fellows:1. The content of soil organic nitrogen, total P, total N, available N and available P under winter potato crop stubble were higher than that of wheat stubble, and the biggest difference were in total P, reached by14.493%, and soil total K and available K were lower than wheat stubble. Potato stubble were higher than that of wheat stubble in soil urease, catalase and phosphatase activity, but lower than wheat stubble in sucrase, by21.642%.2. Maize and sorghum influenced soil fertility by the form of stubbles. Stubble cropping belt increased the content of soil organicsm, total N, available N, K, urease, sucrase, catalase, and sorghum stubble by fertilier effect was better than that of the maize stubble. Among specific stubble, sorghum stubble were higher than maize stubble in total N, available N, P and K, lower in organic matter and total P.3. Relatived to no stubble, soybean stubble increased the content of soil organicsm, total N, P, K, available N, P, catalase, and reduced the content of soil available K, sucrase and phosphate than after crop rotation, sweet potato reduced the content of soil total N, K, available N, P, K, and improved soil organicsm, total P, and the content soil nutrient of soybean stubble were more than sweet potato. Stubble cohesions of wheat season improved the content of soil organicsm, total N, P, K, available N, and phosphatase activity relatived to no stubble cohesion, reduced the content of soil available P, K, urease, sucrose enzyme and catalase activity, and soil fertility of soybean stubble were higher than sweet potato stubble in the way of soil organicsm, total N, K, available K, P, sucrose enzyme and phosphatase. 4. In three different intercropping systems with spring stubble, three strip relay intercropping increased soil organic matter, total N and available nurtient than two stip relay, and wheat/sorghum/soybean were higher than wheat/maize/soybean in organic matter, total N,K, available Nand P. In summer stubble wheat/maize/soybean increased soil nutrient than wheat/maize/sweet potato.5. Analysing the anniversary changes of the soil fertility under different cropping systems, during three years, the content of soil organicsm, total P, available N were on the increase.by3.736%-9.829%,25.434%-63.785%,5.718%～19.133%relatively, total N, available K on the reduce by-6.913%～-10.294%,-34.906%--64.576%. Total K and available P increased at first and then decreased. At the same implant anniversary, the soil nutrient under different cropping systems had the same change. The three relay strip intercropping were higher than two relay in soil organic matter total N and available N, and multiple cropping systems were higher than fallow. In three relay strip intercropping, wheat/sorghum/soybean and wheat/maize/soybean produced the most fertilizer effect in soil organicsm and total N, followed by potato/maize/soybean, the smallest was wheat/maize/sweet potato. In soil total P and available P, potato/maize/soybean was obviousest, the lowest was wheat/maize/sweet potato. Wheat/maize/sweet potato and potato/maize/soybean reduced obviously the content of soil total K and available K, wheat/maize/soybean and wheat/sorghum/soybean was to low consumption. Wheat/maize-fallow land on soil total K and P were lower than wheat-fallow land/soybean, and the amount were0.508%and5.379%, the other were higher than wheat-fallow land/soybean.6. In three relay stripe intercropping, sweet potato being harvested tuber crops, performanced a larger contribution to anniversary yield.Therefore, wheat/maize/sweet potato had maximum anniversary yeild, being39685.69kg/hm2, significantly largher than the other cropping systems, and wheat/maize/soybean had maintained a high annual output, followed by wheat/maize/soybean, wheat/sorghum/soybean was the smalllest. In two ripe intercropping, the yield of wheat/maize was always greater than wheat-soybean. Wheat/maize/soybean with relatively high yield ensured high production value, showing the highest economic benefits, being14196.41yuan/hm2, followed by potato/maize/soybean. Wheat/maize/sweet potato had higher annual yield, but lower prices and growing labor force invesment of the sweet potato exerted an enormous influence, and wheat/maize/sweet potato followed again, the smallest was wheat/sorghum/soybean, only being8904.60yuan/hm2, significantly lower than the other cropping systems.In addition,wheat/maize/fallow land>wheat/fallow land/soybean. In VCR and individual labor income,wheat/maize/soybean was the largest, and wheat/maize-fallow land>wheat-fallow land/soybean.