Effects Of Subsoiling On Soil Properties And Bacterial Community Structure In Black Soil Region

In order to elucidate the mechanism of continuous subsoiling measures on soil quality and bacterial community diversity in black soil,seven treatments were set up from 2016 to 2017: rotary tillage(CK),1 years of surface tillage(QS1),2 years of surface tillage(QS2),1 year of deep subsoiling(SS1),2 years of deep subsoiling(SS2),1 year of extra-deep subsoiling(CS1)and 2 years of extra-deep subsoiling(CS2).The changes of soil physical and chemical characteristics,biological characteristics,and crop yield were studied.The TOPPIC method was used to link the soil indicators to evaluate the effect of deep soil improvement on the soil,and to increase data support for the sustainable use of black soil.The results show:1.Compared with rotary cultivating,subsoiling can significantly reduced soil compaction and bulk density of the plough layer,increased total soil porosity,capillary porosity,and gas-filled porosity,reduced soil solids ratio,and ratio of soil to liquid in the0-20 cm soil layer,improved soil Vapour ratio and proportion of soil liquid in 20-40 cm soil layer.Continuous subsoiling for 2 years treatments produced soil pressure on the20-40 cm soil layer,and the soil porosity showed a downward trend.2.Subsoiling can significantly increase soil saturated hydraulic conductivity in0-20 cm soil layer,and CS2 and QS2 have the best effects in 0-10 cm and 10-20 cm soil layers,respectively.Subsoiling can significantly reduce the surface soil water content of0-20 cm,with SS1 and SS2 as the smallest drop,improving the soil water content of20-40 cm soil layer,with the QS2 effect being the best.The soil water content in subsoiling for 2 years is higher than that in subsoiling for 1 year.The soil temperature of subsoiling treatments was significantly lower than CK at the filling stage,while the soil temperature at jointing stage,tasseling stage,mature stage was significantly higher than CK.With the increasing of the depth of subsoiling,the warming effect of soil surface declined significantly.3.Subsoiling can promote the activation of soil carbon pools,increase the depth of loose soil in 0-20 cm soil layer,increase the activity index of carbon pools,reduce the decline of carbon stock index,and increase the soil carbon pool management index ineach body layer.Continuously subsoiling and reduce the activity index of soil carbon pool in 0-10 cm soil layer,increase the carbon stock index and reduce the carbon stock management index.Compared with rotary cultivating,subsoiling can promoted the accumulation of alkali-hydrolyzable N and available K in the soil.Continuously subsoiling reduced soil available soil nutrients in 0-10 cm soil layer and increased soil available nutrient content in 10-20 cm soil layers.Subsoiling could maintain the long-term soil enzyme activity in 0-20 cm soil layer,increased the soil enzyme activity in 20-40 cm soil layer.4.Subsoiling reduce the microbial biomass nitrogen content in 0-10 cm soil layer and increase the microbial biomass nitrogen content in 10-40 cm soil layer.Soil microbial biomass carbon,microbial quotient,and microbial biomass C/N ratio in 0-20 cm soil layer showed a downward trend with increasing deep soil depth,and 20-40 cm soil layer showed an upward trend.The richness and diversity of bacterial communities in the rhizosphere soil of 0-20 cm soil layers were improved by subsoiling compared with CK.The richness of bacterial communities in subsoiling two years was higher than one year,and CS2 was the best.Subsoiling increased the relative abundance of Acidobacteria,Gemmatimonadetes,Planctomycetes and Thaumarchaeota,reduced the relative abundance of Actinobacteria,Firmicutes.5.Compared with rotary cultivating,subsoiling can promoted the growth and development of the ear and increased the yield.SS2 has the highest yield of corn.Continuously subsoiling reduced the water content of corn kernels,increased the grain weight of corn kernels,and promoted yield increase.Compared with rotary cultivating,subsoiling improves the soil quality evaluation index of 0-40 cm,and the 20-40 cm soil layer is the most significant.SS2 has the highest economic benefits and better soil quality improvement.It is the most suitable subsoiling method in the test area.