Characteristics Of Soil Water Movement And Its Dominant Factors Under Different Management Model In Apple Orchards In The Gully Region Of Plateau

The residual gully area is an important birthplace of dry farming in northern China.Since the implementation of the policy of returning farmland to forests,the local apple industry has been vigorously promoted,the area of apple orchards has grown rapidly,and apple trees have deep roots and strong water consumption by transpiration.The large-scale planting will adversely affect the orchard's ecological and hydrological process.During the growth of fruit trees,water has become a key factor limiting the sustainable development of orchards in the region.The changes in the management methods in the garden have an important impact on the physical and chemical properties of the soil and the movement of water.Based on this,four fruit-crop compound managements including artificial weeding(MO),Malus-Trifolium(M1),Malus-Wild(M2),Malus-Zea(M3)and 4 different amounts of organic fertilizer including 0 t/hm2(T0),6 t/hm2(T1),9 t/hm2(T2),12 t/hm2(T3)apple orchards as research objects.Soil physical and chemical properties,soil infiltration characteristics and preferential flow characteristics were studied.The effects of soil factors such as soil bulk density,particle size composition,and organic matter content on the soil infiltration process were discussed.Based on this,stepwise regression analysis and path analysis were used to screen out the dominant factors of infiltration and preferential flow.It is expected to provide data support for the selection of business models for water saving and emission reduction of apple orchards in the Gully Region of Plateau,and provide theoretical support for the selection of sustainable apple orchard business models.The main research conclusions are as follows:(1)Malus-Trifolium,Malus-Wild,and Malus-Zea were better than those of artificial weeding plots.The physical and chemical properties of soil were also improved with organic fertilizers.The increase in the amount of application showed a greater improvement.According to the US Department of Agriculture system,the apple orchard soil in the remaining gully area is silty sandy soil.(2)The soil infiltration process in the study area can be divided into three parts.The difference between the initial infiltration rate and the stable infiltration rate is obvious.There were significant differences in soil infiltration rates in various types of orchards.The initial infiltration rate and stable infiltration rate of the fruit-growth model were both Malus-Trifolium>Malus-Zea>Malus-Wild>Artificial Weeding.The initial infiltration rate and stable infiltration rate of the orchard soil with different organic fertilizer application rates were 12t/hm2>9t/hm2>6t/hm2>0t/hm2.Three model were used to fit apple orchard infiltration process.It is found that Jiang Dingsheng's model is suitable to describe the change of soil infiltration rate of apple orchard with time in residual gully area.(3)The staining and tracing experiments showed that the matrix flow and preferential flow coexisted during the infiltration process of the apple orchard in the residual gully area.The development degree of soil preferential flow in each compound mode of fruit and farming was Malus-Trifolium>Malus-Zea>Malus-Wild>Artificial Weeding;the development degree of soil preferential flow in orchards with different organic fertilizer application rates was 12t/hm2>9t/hm2>6t/hm2>0t/hm2.The treatment of orchard grass and increased application of organic fertilizer can reduce rainfall evaporation and increase rainfall utilization.The wet front that moves faster downwards is saturated,and the soil around the wet peak is saturated and flows sideways.Guide water redistribution,make the apple orchard soil profile water distribution more uniform,and have a certain elimination effect on soil desiccation.Logistic function,linear function,exponential function,and quadratic function were selected to perform regression analysis on the soil area staining ratio of the apple orchard and its corresponding soil layer depth.It was found that the two followed the law of Logistic function.(4)The principal component analysis results showed that soil factors can be summarized into three principal components,the first principal component is composed of soil water holding capacity and soil nutrients,and the second principal component is composed of bulk density and particle size composition.The third principal component is total porosity.Path analysis results show that total porosity is the main decision factor affecting the initial soil infiltration rate,and silt content is the main limiting factor that affects the initial soil infiltration rate.Sand content is the main decision factor affecting soil infiltration rate,and bulk density is the main limiting factor affecting soil infiltration rate.Total porosity is the main decision factor affecting soil dyeing area ratio,and bulk density is the main limiting factor affecting soil dyeing area ratio.Growing grass in the orchard and adding organic fertilizer can convert more rainfall into soil water,which is a successful way to save water and reduce emissions in apple orchards in the Gully Region of Plateau.It is of great significance to the sustainable development of the apple industry.