Study On Soil Fertility Improvement Of Eroded And Degraded Black Soil

Northeast black land is a valuable land resource,which plays an important role in ensuring China’s food security.However,due to the special climate,soil,topography and human factors,the problem of soil erosion and degradation appears in the black land.In order to slow down soil erosion and degradation of black land and improve farmland fertility.Through indoor simulation and field observation,the effects of soil erosion and land use pattern on soil water and gas transport characteristics were studied,and the characteristics of air permeability and relative gas diffusion were analyzed.Finally,the method of adding woody peat and bentonite to eroded and degraded farmland for improving fertility rapidly was put forward.The results of this study are as follows:(1)Compared with ungraded farmland,the bulk density of light,moderate and serious erosion farmland increased,the saturated hydraulic conductivity decreased by84.4%,53.7% and 12.7%,the air permeability decreased by 94.6%,64.4% and 14.0%,and the relative gas diffusion decreased by 91.3%,82.6% and 4.3%,respectively.In addition,the saturated hydraulic conductivity,air permeability and relative gas diffusion of pine forest land,seabuckthorn forest land and abandoned land also decreased.The order of soil water holding capacity was ungraded farmland > pine forest land > light erosion farmland > moderate erosion farmland > abandoned land > seabuckthorn forest land > serious erosion farmland.Soil water holding capacity decreased with the increase of soil erosion degree,and there was a significant negative linear correlation between soil water holding capacity and bulk density and sand content.The results showed that the soil water and gas transport performance of ungraded farmland,seabuckthorn forest land and abandoned land was better.Planting soybean and seabuckthorn or abandoned land could improve the soil water infiltration rate,reduce surface runoff and slow down soil erosion.(2)With the increase of soil water content,soil air permeability and relative gas diffusion decreased under different land use patterns and with the addition of woody peat and bentonite,and changed rapidly in the range of low water content,but slowly in the range of high water content,and finally tended to be flat.There were significant differences in soil air permeability and relative gas diffusion between the vertical and horizontal directions of ungraded farmland,pine forest land and abandoned land,and there were anisotropy in soil air permeability and relative gas diffusion.There is a significant linear correlation between the logarithm of saturated hydraulic conductivity and air permeability or relative gas diffusion measured under different land use patterns,which can be used to estimate soil saturated hydraulic conductivity.(3)The results showed that the saturated hydraulic conductivity,air permeability,relative gas diffusion,organic carbon content and the yield of potted maize increased with the addition of woody peat in laboratory simulation;the saturated hydraulic conductivity,air permeability and relative gas diffusion decreased with the addition of bentonite or the mixed addition of woody peat and bentonite,but the organic carbon content and the yield of potted maize increased.The soil saturated hydraulic conductivity,relative gas diffusion,organic carbon content and soybean yield increased by 75.0%,32.0%,36.1% and 43.2% respectively,while the air permeability decreased;the soil saturated hydraulic conductivity,air permeability and relative gas diffusion decreased,but the organic carbon content and soybean yield increased with the addition of bentonite;The soil saturated hydraulic conductivity,relative gas diffusion,organic carbon content and soybean yield were increased by 134.4%,28.0%,36.0% and 26.3%respectively by adding woody peat and bentonite.The addition of woody peat and bentonite could improve the soil water holding capacity,and the decomposition of organic carbon slowed down.In a word,the effect of mixed addition of woody peat and bentonite is the best,which can effectively improve the soil ventilation and water permeability,water holding capacity,organic carbon content and crop yield,and contribute to the accumulation of organic carbon in the soil.It is a feasible measure to rapidly improve the degraded black soil.