Effect Of Hedgerows On Soil Microbial Characteristics On Slope In Purple Soil Area

Effect of hedgerow on soil organic carbon and soil microbial indicators of surface soil on different land utilization patterns and slopes in purple soil area are investigated, which is beneficial for multiple utilization and reconstruction of slope in purple soil area. Based on standard cell observation method and indoor experiments, effect of Leucaena leucocephala and Vetiveria zizanioides (planting since April 2010) on number of microorganisms, microbial biomass, soil organic carbon content and soil organic carbon conservation in surface soil and influence on controlling on slope erosion, agricultural non-point source pollution and improving soil fertility and preventing soil degradation are investigated. The results show that:(1) Planting of Leucaena leucocephala and Vetiveria zizanioides hedgerow can increase thenumber of bacteria, actinomycetes and fungi in the soil. Effect of Vetiveria zizanioides hedgerow on the number of soil bacteria, actinomycetes and fungi is higher than effect of Leucaena leucocephala hedgerow. Slope has a greater impact on the number of soil bacteria, actinomycetes and fungi, and the increase of slope can reduce the number of soil bacteria, actinomycetes and fungi. The number of soil bacteria, actinomycetes and fungi downhill are higher than that of uphill in all plots, and the number of soil bacteria, actinomycetes and fungi of sampling point near to hedgerow fence downhill are greatly higher than that of other sampling points. As there is no different between soil physical and chemical characteristics of sampling points uphill, and without influence of hedgerow, the number of soil bacteria, actinomycetes and fungi of sampling points uphill show little different. Soil microbe, a reservoir of soil nutrients, is the power of organic matter turnover, and planting of Leucaena leucocephala and Vetiveria zizanioides hedgerow are beneficial for the storage of soil nutrients.(2) Soil organic carbon content and soil organic carbon density of plots with Leucaena leucocephala and Vetiveria zizanioides hedgerow are significantly higher than that of corresponding control. Effect of Leucaena leucocephala on the increase of soil organic carbon content and soil organic carbon density is consistent with that of Vetiveria zizanioides.The gentler slope is beneficial for the increase of soil organic carbon content and soil organic carbon density. Under the same treatment, accumulation of soil organic carbon downhill is more significant than that of uphill, and soil organic carbon content and soil organic carbon density of sampling point near to hedgerow fence downhill are greatly higher than that of other sampling points. It is mainly due to the decrease of soil nutrient uphill caused by runoff on slope. On the other hand, as cover of Leucaena leucocephala and Vetiveria zizanioides hedgerow can block sediment loss of topsoil, enriching soil nutrient downhill, and cover of hedgerows and increase of soil organic matter improving soil permeability, downhill is more conducive to the accumulation and organic matter and strengthening of decomposition. As there is no different between soil physical and chemical characteristics of sampling points uphill, and without influence of hedgerow, soil organic carbon of sampling points uphill show little different as a whole.(3) Soil microbial biomass carbon and nitrogen of plots with Leucaena leucocephala and Vetiveria zizanioides hedgerow are significantly higher than that of corresponding control. Planting of Leucaena leucocephala and Vetiveria zizanioides hedgerow can significantly increase soil microbial biomass carbon and nitrogen in the soil. Average microbial biomass carbon of all sampling points of plot with Vetiveria zizanioides is higher than that with Leucaena leucocephala, which is consistent with variation of number of soil microbe. After planting of Vetiveria zizanioides, soil microbial biomass carbon and nitrogen of 10°plot are higher than that of 15°plot. Accumulation of soil microbial biomass carbon and nitrogen downhill is more significant than that of uphill. The soil microbial biomass is the outer expression for microbial growth, retention, death, mineralization and release of soil nutrient. Planting hedgerow can increase soil microbial biomass, and nutrient immobilization and mineralization release maintain at a fairly high level, effective enhancing soil fertility.(4) Soil microbial quotient of plots with Leucaena leucocephala and Vetiveria zizanioides hedgerow are significantly higher than that of corresponding control. Soil microbial quotient of plots with Vetiveria zizanioides is higher than that of plot with Leucaena leucocephala hedgerow significantly, meaning that effect of Vetiveria zizanioides on maintenance of microbial biomass is more significant than that of Leucaena leucocephala. After planting Vetiveria zizanioides hedgerow, soil microbial quotient of 10°plot are higher than that of 15°plot. Accumulation of soil microbial quotient uphill is more significant than that of downhill, which is different from variation of microbial biomass carbon and organic carbon.(5) Planting Leucaena leucocephala and Vetiveria zizanioides hedgerow can significantly increase the soil basal respiration rate. Effect of Leucaena leucocephala on enhancement of soil basal respiration rate is consistent with that of Vetiveria zizanioides. After planting Vetiveria zizanioides hedgerow, soil basal respiration rate of 10°plot is higher than that of 15°plot. Accumulation of soil microbial quotient downhill is more significant than that of uphill.(6) Soil metabolic quotient of plot without hedgerows is significantly higher than that with Leucaena leucocephala and Vetiveria zizanioides hedgerow, which is inconsistent with variation of soil microbial quotient, soil basal respiration rate and other indicators. Effect of Leucaena leucocephala on soil metabolic quotient is consistent with that of Vetiveria zizanioides hedgerow. After planting Vetiveria zizanioides hedgerow, soil metabolic quotient of 10°plot is lower than that of 15°plot, which means that slope affect on utilization ratio of soil organic carbon significantly. There is little difference between soil metabolic quotient uphill and that of downhill, meaning that effect of hedgerow on utilization ratio of soil organic carbon uphill is consistent with that downhill.