Effects Of Returning Organic Material To Field Under Different Tillage Measures On Soil Physical Properties

Black soil is a kind of soil with good properties,high fertility and very suitable for plant growth.It is a very precious wealth endowed by nature to human beings.There are only three large areas of black soil in the world,one of which is in the northeast of China.However,due to the increasing soil erosion and the long-term overload of human use,the superior conditions of black soil are gradually destroyed,organic matter content is gradually declining,physical and chemical properties and ecological functions are gradually degraded,which has seriously affected the sustainable development of agriculture in Northeast China.The economic development of Northeast China mainly depends on agriculture,and Northeast China is also the granary of the whole country.Protecting and improving the quality of cultivated land in black soil is the basis of keeping the strategic bottom line of "basic self-sufficiency of grain and absolute security of rations".It is also an important guarantee for national food security and ecological environment restoration.Aiming at the problems of black soil fertility and org anic matter reduction in Northeast China,six treatments were set up in the typical black soil area of Nenjiang County,Heilongjiang Province.They are:(1)No-tillage control(NT);(2)No-tillage + straw returning(NTS);(3)No-tillage + organic fertilizer(NTM);(4)Deep-tillage control(DT);(5)Deep-tillage + straw returning(DTS);(6)Deep-tillage + organic fertilizer(DTM).The effects of straw and organic fertilizer on soil physical properties and soybean root system under no-tillage and deep ploughing conditions were studied,which provided theoretical basis for the conservation and improvement of black soil fertility and the sustainable utilization of crop growth conditions.The main results were as follows:(1)Under different tillage practices(deep tillage and no-tillage)without organic materials,the effect of deep tillage on reducing soil bulk density by 10-20 cm was the most obvious.The soil porosity,saturated water conductivity and field water holding capacity were increased,and the solid and liquid phases of soil were increased,and the soil vapor phase ratio was reduced.Deep tillage can effectively improve the physical structure of soil.(2)Under no-tillage conditions,the application of organic materials has an effect on soil bulk density,porosity,field water holding capacity,saturated water conductivity,three-phase ratio and aggregates and other physical properties.Compared with the control,returning organic materials to the field can reduce soil bulk density of 10-20 cm soil layer,but there is no significant change in soil bulk density below 20 cm.With the increase of soil porosity and straw returning,soil water holding capacity and saturated water conductivity can be increased.With the increase of soil depth,soil solid fraction can be reduced,and soil liquid fraction and vapor fraction can be increased.(3)The application of organic materials under deep ploughing conditions has great influence on the physical properties of soil,such as bulk density,porosity,field water holding capacity,saturated water conductivity,three-phase ratio and aggregates.Deep turning of organic materials in 0-10 cm soil layer has obvious effect on reducing soil bulk density.With the deepening of soil layer,although soil bulk density tends to increase,the reduction of soil bulk density is significantly better than that of deep turning control.The effect of improving soil porosity is good.Deep ploughing organic materials can improve field water holding capacity and saturated water conductivity in different soil layers.Deep ploughing straw returning and deep ploughing organic fertilizer treatment can reduce the solid and liquid phases of soil and improve the gas phase ratio of soil.(4)Under no-tillage and deep ploughing conditions,the app lication of organic materials can promote the growth of soybean root system,expand root surface area,and increase the area of nutrient and water uptake by roots,thus laying a good environment for the subsequent growth and development of plants.Among them,deep ploughing can promote root growth better than no-tillage,and can absorb more nutrients and water from the soil.