Effects Of Soil Erosion Intensities On Mollisols Physical And Chemical Properties And Field Productivity

The region of Mollisols in Northeast China is very important to the grain productivity.Mollisols erosion greatly affects agricultural sustainable development.In past decades,many studies have been conducted to evaluate soil removal and mollisols physical properties,but less on the field scale involving the effects of mollisols sediment deposition on mollisols physical properties and mollisols productivity.However,very few studies focused on the impact of mollisols erosion on crop productivity in different soil layers in China.To investigate the effects of soil erosion intensities on soil physical and chemical properties of soil and crop yield,a simulated field experiments were conducted in topsoil(30 cm),transition layer(40 cm)and parent material layer(> 70 cm)of Mollisols farmlands.Five erosion treatments,including 70 cm topsoil removal,30 cm topsoil removal,no eroded soil,30 cm sediment deposition and 70 cm sediment deposition were set respectively.Each erosion level had two sub-treatments: conventional fertilization and no fertilization.The main results were as follows:(1)Erosion intensities had a significant effect on the soil structure and its function of the Mollisols farmland.Compared with no eroded soil,soil bulk densities of the other four treatments were all significantly increased in the plowed layer(0 ~ 20 cm),while soil porosities,contents of soil water stable aggregates were greater than 0.25 mm,mean weight diameters,geometric mean diameters,field capacities,Saturated moisture and soil organic matter contents of the four treatments were all significantly decreased.The effect of soil erosion intensities on soil structure and function,soil bulk density had seasonal variation Soil bulk density increased in July and August,soil porosity,soil organic matter content and moisture decreased.Chemical Fertilizer application could improve soil porosities,lightly increased soil aggregate stability,water content and soil organic matter content,but could not recover deterioration of soil structure and function to the pre-erosion level.The soil erosion intensities had a significant influence on many important indicators of soil structure and function indices.Soil organic matter content,soil porosity,soil water stable aggregates larger than 0.25 mm,mean weight diameters,geometric mean diameters,field capacities decreased,whereas soil bulk density increased with the soil erosion intensities increased.(2)Soil erosion changed the soil nutrient status.Compared with no eroded soil,soil total nitrogen,total phosphorus,available nitrogen of the four treatments significantly decreased in removal,30 cm topsoil removal,and 70 cm sediment deposition significantly decreased.Fertilization could reduce the decline induced by soil erosion.The soil erosion intensities had a significant influence on many important indicators of soil nutrient indices,such as soil total nitrogen,total phosphorus,available nitrogen,available phosphorus,available potassium.(3)Both soil topsoil removal and soil sediment deposition impacted on crop yields.Soil erosion intensities resulted in decrease plant height,crop biomass and yield.Compared with no eroded soil in no chemical feitiler application block,corn yields of the treatment of 30 cm topsoil removal,70 cm topsoil,70 cm sediment deposition reduced by 71.8%,88.1% and 23.2%,respectively;soybean yields of the treatment of 30 cm topsoil removal,70 cm topsoil was reduced by 43.3% and 46.4%,respectively.In the chemical fertilizer application block,the decrease of corn seed yield lower down,and there was no significant difference in soybean yield.Compared with no eroded soil in feitiler application block,corn yields of the treatment of 30 cm topsoil removal,70 cm topsoil and 70 cm sediment deposition was reduced by 42.1%,52.6% and 12.4%,respectively.Corn yields of the treatment of 30 cm sediment deposition increased 13.3%.Compared with no eroded soil,soybean yields of the treatment of 30 cm topsoil removal and 70 cm topsoil reduced by 43.4% and 46.4%,respectively.Fertilization could improve the reduction of crop yield induced by soil erosion.Plant height and crop biomass showed an increase with the growth season.Compared with no chemical feitiler application block,plant height of corn and soybean in September were 16.7~26.1 times and 8.70 ~ 12.5 times higher than that in June.Compared with crop biomass in June,crop biomass of corn and soybean in September increased 115.3 ~ 456.9 times and 30.5 ~ 82.4 times.Compared with feitiler application block,plant height of corn and soybean in September were 13.4 ~ 28.2 times and 9.5 ~ 12.6 times higher than that in June.Compared with crop biomass in June,crop biomass of corn and soybean in September increased 193.8 ~ 997.0 times and 193.8 ~ 997.0 times.Thus,soil erosion,no matter topsoil removal or sediment deposition,both led to the decline of soil organic matter,total nutrients,available nutrients,and deterioration of soil physical indicators,and crop yield was decreased.The soil erosion induced by fertilization mainly causes the reduction of soil nutrient content,which leads to the decrease of the stability of soil aggregates,which ultimately leads to a reduction in maize yield.However,the effect on soybean yield depends mainly on the stability of soil aggregates.