Effects Of Addition Of Exogenous Organic Matter On Water Characteristics And Crop Yield Of Eroded Degraded Black Soils

Northeast black soil area is one of the main grain production areas in our country,it is a“stabilizer” and "ballast stone" to guarantee food security.However,due to the special geographical climate environment and human unreasonable production and management activities,the phenomenon of soil and water resource loss in the sloping farmland in this region is becoming increasingly serious,leading to the thinning of the black soil layer and the destruction of soil structure.In addition,the black soils is sticky and heavy,which leads to the weakening of soil infiltration capacity,the reduction of soil water holding capacity and water supply capacity,and the decline of land productivity.This poses a serious threat to national and regional food security and sustainable agricultural development.Therefore,applying different organic materials(straw,biochar,PAM and total nutrient water soluble fertilizer)to soil to improve soil structure is of great significance to improve soil water characteristics,water utilization rate and land productivity.In order to reveal the influence of different organic materials(straw,biochar,PAM and total nutrient water soluble fertilizer)on soil water characteristics and land productivity,In this paper,the saturated hydraulic conductivity,water holding capacity and water supply capacity of sloping black soil with light,medium and heavy erosion were studied,VG model was used for fitting,and the correlation between them and soil physical and chemical properties was discussed,so as to explore the influence of erosion degradation on soil water characteristics of sloping black soil;Studying the influence of different organic materials on soil structure by measuring soil aggregates under different organic materials,and analyzing the distribution of soil aggregates,the content of >0.25 mm water stable aggregates,average weight diameter and geometric mean diameter.By measuring soil saturated hydraulic conductivity under different organic materials and conducting correlation analysis,stepwise regression analysis and path analysis on soil physical and chemical properties and saturated hydraulic conductivity,the influence of different organic materials on soil infiltration performance and its main influencing factors were studied.By measuring soil water characteristic curves under different organic materials and analyzing VG model fitting parameters,the effects of different organic materials on soil water retention and water supply capacity were explored.By measuring the plant height,stem diameter,dry matter accumulation and yield of corn and soybean under different organic materials during the growth period,the effects of different organic materials on the growth and development of crops were investigated.This provides reference and theoretical basis for applying different organic materials to improve soil structure and infiltration performance,soil water retention performance and land productivity in the study area.The main research achievements of this paper are as follows:(1)The erosion degradation of sloping black soils made the soil texture coarser,the contents of organic matter and >0.25 mm water stable aggregates decreased and the soil bulk density increased,which led to the decrease of soil saturated hydraulic conductivity and the weakening of soil water holding capacity and water supply capacity.The increase of soil bulk density and the decrease of contents of organic matter and >0.25 mm water stable aggregates were the main factors leading to the decrease of soil water holding capacity.(2)Different organic materials increased the content of >1 mm water-stable aggregates,especially significantly increased the content of >2 mm water-stable aggregates,thus enhancing the stability of soil structure.The application of biochar and total nutrient water soluble fertilizer in all organic materials had the best effect on improving soil structure,among which the application of Y3 and O1 showed the best performance.(3)The application of different organic materials can improve the soil water characteristics,among which the best effect is biochar,followed by total nutrient water soluble fertilizer.The improvement effect of Y3(22500 kg/ha)in biochar was slightly better than that of Y2(15000 kg/ha),and O1(1100 kg/ha)in total nutrient water soluble fertilizer was the best.Soil saturated hydraulic conductivity and water supply capacity were mainly affected by organic matter content and bulk density,and had extremely significant positive correlation with organic matter content and extremely significant negative correlation with bulk density(P<0.01).Soil water holding properties were mainly affected by >0.25 mm water stable aggregates and soil mechanical composition,and were significantly positively correlated with >0.25 mm water stable aggregates and silt content(P<0.01).(4)Biochar,total nutrient water soluble fertilizer,PAM and straw can promote the growth of maize and soybean,improve crop yield and water yield efficiency.Biochar(Y2)>total nutrient water soluble fertilizer(O1)> straw(B1)> PAM(P3)> straw(S2).The order of improving water production efficiency was biochar > total nutrient water soluble fertilizer >PAM> straw,and there was no significant difference in water production efficiency between PAM and straw.Considering the improvement effects of different organic materials on soil structure,water characteristics and crop growth,as well as economic benefits,the best application of biochar was followed by the application of total nutrient water soluble fertilizer,which was Y2(15000 kg/ha)and O1(1100 kg/ha),respectively.