Effects Of Interplanting Herbage On Soil Microbial Biomass Carbon And Nitrogen In Weibei Apple Orchard

Weibei Loess Plateau is one of the high quality apple producing areas in China the world. Interplanting herbages is a soil management mode commonly employed for orchard development in developed countries. It has been promoted as a measure of green fruit producing in China since 1988. Current research on intercropping herbages in orchard mainly focus on the effects of growing herbage on fruit yield, fruit quality, microclimate, and soil environment, while little work was done on the mechanisms. Intercropping herbages in apple orchard in Weibei Area was studied. Through field experiments and laboratory analysis, soil microbial biomass carbon(SMBC), soil microbial biomass nitrogen(SMBN) were analyzed, and responses of them to intercropping herbages were discussed. This research provided a scientific basis for studying the interaction mechanisms between fruit trees and herbages in the fruit orchard-growing herbage complex system. The main results showed that:1.Interplanting herbages significantly improved the soil structure in apple orchards, effectively reducing the soil of soil bulk density in 0~40cm. Interplanting erbage improved the nutrient content of topsoil, and significantly increased the content of soil organic carbon and total nitrogen. Compared with clear tillage, the content of soil organic carbon and total nitrogen in interplanting herbages could improve by 13.4%~68.6% and 10.4%~43.4%. In different growing seasons, the overall trend showed summer>autumn>spring, in the vertical distribution among treatments, the content of soil organic carbon and total nitrogen was highest in topsoil(0~5cm), which was decreased with depth.2.Interplanting herbages effectively improved the soil enzyme activity of catalase, urease, sucrose and cellulose. Interplanting Trifolium repens L. and Lotuscorniculatus L. were better than other treatments. With the season change, the trends of soil enzyme activity showed that it decreased at first and increased at last, and it reached maximum in summer. The activity of soil enzyme was decreased with soil depth.3.Interplanting herbages significantly increased the content of soil microbial biomass carbon(SMBC) and nitrogen(SMBN), ratio of SMBC to soil organic carbon(q SMBC), ratio of SMBN to soil total nitrogen(q SMBN). It improved the utilization efficiency of soil organic carbon and total nitrogen for microbe. In different seasons, the overall trend showed summer>autumn>spring. The contents of them were decreased with soil depth. In the topsoil of 0~5cm, the content of soil microbial biomass carbon in the interplanting Trifolium repens L. treatment was highest among of all treatments. In spring, summer and autumn, its contents were increased by 175.2 percent, 144.9 percent and 175.4 percent. The distributions of q SMBC was different in different treatment. The most obvious effect arose in interplanting Trifolium repens L. and Lotuscorniculatus L.and Dactylis glomerata L. treatmens. In the topsoil of 0~20cm, the content of soil microbial biomass nitrogen in the interplanting Trifolium repens L. treatment was highest among of all treatments. In spring, summer and autumn, compared with clear tillage, its contents were increased by 62.4 percent, 65.3 percent and 72.6 percent.Like the q SMBC, the distributions law of q SMBN was not obvious in different treatment. Interplanting Trifolium repens L. and Lotuscorniculatus L. were higher than other treatments. In the topsoil(0~5cm), the ratio of soil microbial biomass carbon to soil microbial biomass nitrogen were the highest in the all treatments. In the 0~40cm soil layer, the ratio of soil microbial biomass carbon to soil microbial biomass nitrogen were decreased with soil depth.4.Correlation analysis showed that soil microbial biomass carbon had significant correlation extremely with soil microbial nitrogen, and it had significant correlations with soil organic carbon, total nitrogen, sucrase, urease and cellulase, but it had no significant correlation with soil catalase. Path analysis indicated that soil organic carbon, total nitrogen and cellulase were the important factors that affected the soil microbial biomass carbon, and soil total nitrogen and urease were the important factors that affected the microbial biomass nitrogen.