Erosive Degradation And Suitability Diagnosis Of Cultivated-layer Quality Of Purple Soil Sloping Farmland

Purple soil slope farmland is an important farmland resource in southwest my country,which has the characteristics of high productivity and strong erodibility.Soil erosion is the main reason for the degradation of sloping farmland,soil erosion and productivity decline,and has great potential danger to the sustainable use of slope farming.The soil of sloping farmland is not only the basis of agricultural production,but also the object of soil erosion.Understand the morphology and physical and chemical characteristics of the cultivated layer of sloping farmland,study the influence of soil erosion on the geographical characteristics of cultivated land,and establish a reasonable minimum data set for the evaluation of cultivated layer.Purple soil sloping farmland,analyzing the relationship between crops and soil suitability,and clarifying the factors that hinder the soil quality of the sloping farmland,can provide an important basis for evaluating and controlling the reasonable farming layer of the sloping farmland.This paper takes purple soil slope farmland as the research object,and analyzes the cultivated layer architecture characteristics of purple soil slope farmland with different degrees of erosion through small watershed survey of field slope farmland and shovel erosion simulation plot.Through field surveys and indoor physical and chemical experiments,the changes in the physical and chemical properties of purple soil sloping fields with different degrees of erosion in 2018 and 2019were analyzed,and the effect of soil erosion on the physical and chemical properties and soil quality of purple soil sloping fields with different degrees of erosion was explained.,Analyzed the relationship between soil degradation and erosion resistance of slope farmland with different degrees of erosion.The soil quality obstacle factor diagnosis model is used to analyze the obstacle degree of soil indicators,and the regulation method is proposed according to the obstacle type.The degree and applicability of coupling and coordination between crops and cultivated layers of purple soil sloping farmland with different degrees of erosion were analyzed using the model of the degree of coupling and coordination of cultivated layer.（1）The quality of the cultivated layer of purple soil slope farmland is significantly affected by the evaluation method and environmental factors.The determination coefficient of the weighted summation method is greater than that of the weighted comprehensive method（0.6743>0.3324）.When the weighted summation method evaluates the quality of the cultivated layer,the MDS evaluation result is closer to TDS.The summation method is suitable for the quality evaluation of the cultivated layer of purple soil slope farmland.The purple soil sloping farmland has a significant correlation between environmental factors and farm layer quality indicators.Effective soil layer thickness is positively correlated with silt and organic matter,altitude,slope position and saturated hydraulic conductivity are negatively correlated;slope is negatively correlated with bulk density,cultivated layer thickness and clay particles,and effective soil layer thickness has an impact on cultivated layer quality indicators The most significant.The correlation order of environmental influencing factors of purple soil slope farmland is effective soil thickness>slope position>altitude>slope.Effective soil thickness has become an important environmental factor for improving the quality of cultivated layer.（2）The soil properties of the purple soil slope farmland change significantly with the increase of the degree of erosion,and the physical properties of the purple soil slope farmland change significantly.With the increase of the erosion degree in 2018 and 2019,the bulk density and sand content gradually increase,and the soil powder Grain,clay content,total porosity,capillary porosity,initial infiltration rate,stable infiltration rate,average infiltration rate,saturated hydraulic conductivity show a gradual decrease trend;clay particles,powder particles,bulk density,shear strength,Soil compactness and penetration resistance increase with the increase of erosion depth.The initial infiltration rate,stable infiltration rate,average infiltration rate,and saturated hydraulic conductivity decrease with the increase of soil depth.The chemical properties of purple soil sloping farmland have changed significantly.In 2018 and 2019,organic matter gradually increased with the degree of erosion.On the whole,the content of soil organic matter in the 20-40 soil layer was lower than the 0-20 soil layer,and the p H and cation exchange capacity increased with the degree of erosion The increase gradually decreases.Under different erosion levels,the p H and cation exchange capacity increase with the increase of soil depth.The soil total nutrient and available nutrient gradually decreased with the increase of erosion degree.The total nutrient of the soil decreases with the increase of soil depth less than the available nutrient of the soil.In 2018 and 2019,the characteristics of soil degradation index change under different erosion levels were F_-0>F_-5>F_-10>F_-15>F_-20,and the soil degradation index increased with the increase of erosion degree.For different erosion levels,the soil degradation index increased first and then decreased with the increase of soil depth.The 0-10 soil degradation index was all higher than 30-40 cm.The F_-20 soil degradation index was the largest in 2018 and 2019.The degree is serious.（3）The impediment degree of purple soil slope farmland with different ages and different degrees of erosion is significantly different.In 2018,F_-20’s available potassium and total phosphorus barriers are at a moderate barrier,and F_-20’s total potassium barriers are at a moderate barrier in 2019.Total porosity,saturated hydraulic conductivity,organic matter,CEC,total nitrogen,total potassium,The obstacle degree of total phosphorus decreases with the increase of erosion degree,and the obstacle degree of initial infiltration rate,stable infiltration rate,soil compactness,shear strength,and p H increases with the increase of erosion degree.In 2019,F_-20 is mainly nutrient-poor.The main obstacles are higher cation exchange capacity,clay content,lower total potassium,saturated hydraulic conductivity,and total porosity.Under the same management measures,the clay barrier degree decreases with the increase of erosion degree.Under the same erosion degree,the barrier characteristics of clay,cation exchange capacity,and total potassium are shown as:BF>F>CK,when the erosion degree is greater than 10,The curved surface is steeper,indicating that a higher degree of erosion has a stronger influence on the degree of clay obstruction.Under the same management measures,the cation exchange capacity and the barrier degree of total potassium decrease with the increase of erosion degree,and the total porosity and saturated hydraulic conductivity barrier degree increase with the increase of erosion degree.（4）The degree of crop-crop layer coupling in purple soil is significantly affected by the degree of erosion and management measures.The two-year comparison shows that crops are more sensitive than the crop layer,and crops have a hysteresis effect compared to the crop layer.In 2018,F_-0,F_-5,F_-15,and F_-20 sloping farmland were on the verge of dysregulation and decline in crop gains and losses.In 2018,there were two types of crop gains and losses（80%）and crop lagging（20%）.In2019,the synchronous crop layer accounted for 40%,and the crop loss and loss accounted for 60%.The crop is more sensitive than the crop layer.In 2018,F_-15 and F_-20 are in a mildly declining crop-plow layer co-loss type.The degree of crop-arable layer coupling and coordination is F_-10（0.637）>F_-5（0.482）>F_-0（0.479）>F_-15（0.464）>F_-20（0.381）,crop-arable layer coupling and coordination The degree characteristics are"inverted V-shaped",and the crop-arable layer coupling coordination degree decreases as the degree of erosion increases.F_-0,F_-5,F_-15,F_-20 are on the verge of dysregulation and decay crops-cultivated layer co-damage type,F-10 is in the lagging type of barely coordinated development of cultivated layer,which is not suitable for crop growth.In 2019,the crop-arable layer coupling coordination degree C_d is F_-0（0.538）>F_-5（0.518）>F_-10（0.427）>F_-20（0.317）>F_-15>（0.314）,and crops—The degree of coupling and coordination of the cultivated layer,Cd,decreases firstly and then increases with the increase of the degree of erosion,with a"V-shaped"change characteristic.F_-0 and F_-5 are in the crop-arable layer synchronous type of barely coordinated development,which is barely suitable for crop growth,and F_-10,F_-15,F_-20 have mildly degraded tillable layer co-damage type.In 2018,the effect of biochar+chemical fertilizer on the comprehensive evaluation index of the arable layer was higher than that of chemical fertilizer alone,and the application of chemical fertilizer alone reduced the crop evaluation index,while biochar+chemical fertilizer improved the crop evaluation index and the coordination of crop-crop layer coupling.And the effect of biochar is remarkable.Biochar has a certain influence on the evaluation index of improved crops and the coordination degree of crop-arable layer coupling.In 2019,the comprehensive quality index PCE,crop evaluation index CCE,and crop coupling degree C_d are affected by fertilization higher than that of biochar+chemical fertilizer,and the recovery time of biochar on crops and crops is longer than that of chemical fertilizer（5）At the plot scale,purple soil suitability has a strong association with soil degradation,barrier factors.The soil degradation index is equally divided into 6 levels,which are level I suitable,level II improvement,restoration status,level III no degradation,level IV light degradation,level V moderate degradation,and level VI severe degradation.The crop-cultivation layer coordination degree is divided into 5 levels,which are highly unsuitable,moderately unsuitable,barely suitable,moderately suitable,and highly suitable.All in this article are barely appropriate.Soil bulk density is too large for CK,F,and BF treatments.Under CK treatment,soil saturated hydraulic conductivity,organic matter,and available phosphorus content are far below the appropriate value,which is not enough for crops to grow enough water and nutrients;under F treatment,Soil saturated hydraulic conductivity,organic matter,and available phosphorus are still lower than the appropriate values;under BF treatment,the soil sand content of the cultivated layer is generally within the appropriate value range.The application of chemical fertilizers and biochar+chemical fertilizer treatments have a regulatory effect on various soil attribute indicators.Subsoiling measures can improve the sticky-heavy compaction barrier farm layer and the water-restricted farm layer,reduce the soil erosion of the sloping farmland,and improve the quality of the farm layer.Biochar measures and no-tillage measures for accumulation of soil can improve the nutrient-poor barriers of the cultivated layer.