农牧交错带退耕还草对土壤微生物量CN的影响

Microbial Biomass C,N in Soils in Agro-Pastoral Transitional Zone A fter Alteration of Cropland to Grassland

在农牧交错带以小麦为对照,研究了退耕还草对土壤微生物量C、N的影响。结果表明,0～20cm土层微生物量C、N的大小顺序为:混播草地>相应的单播草地>小麦地。不同单播处理对土壤0～20cm微生物量C、N影响明显。无芒雀麦+冰草(1∶1)在增加土壤微生物量C、N方面效果较佳。一个生长季结束后,单播牧草比小麦能更好地提高土壤的微生物量C、N。

Agro-pastoral transitional zone in China belongs to grassland eco-system in nature. However, fertility of soil in this area becomes less and le ss because of more and more population and reclamation. We were comparing a soil from grassland that had been transformed from cropland with a plot of wheat fie ld in a agro-pastoral transitional zone, aiming to reveal the effects on soil microbial biomass C, N of grassland returned from cropland. The experiment was c onducted at Yuershan pasture of Fengning county of Hebei province in 2000 and 20 01. Siberian wildrye, wheatgrass, sainfoin and smooth bromegrass were chosen acc ording to natural conditions in the experimental area to establish single sowing grassland and mixed sowing grassland. The study results showed that:(1) The ord er of the contents of microbial biomass C, N in 0～20 cm soil layer was mixed s owing grassland> single sowing grassland>wheat field and different single sowing treat had different effects on the contents of microbial biomass C, N in the de pth of 0～20 cm, sainfoin pasture and Smooth bromegrass pasture had the highest contents of microbial biomass C, N in the 2 year's experiment. Different mixing cultivation and combination had greater effects on soil microbial biomass C, N. Smooth bromegrass+Wheatgrass (1:1) could improve the level of microbial bioma ss C, N better. (2) After a growing season, single sowing forages could increase the microbial biomass C, N in the soil more than wheat. In the 0～20 cm soil l ayer, the average contents of microbial biomass C of single sowing grassland wa s four times more than that of wheat field, and the average contents of microbia l biomass N of the sowing grassland increased more than wheat field by 9.91 mg· kg-1.