| As a direct source of plant water demand,soil moisture is the main limiting factor for plant growth on the Loess Plateau of western Shanxi Province.It is also the direct target of moisture competition between apple trees and crops of the apple-crop intercropping systems in this area,which seriously restricts the productivity of the intercropping systems,and some extensive management technology lead to intense interspecific soil moisture competition of the apple-crop intercropping systems,which affects the functions and benefits of the apple-crop intercropping systems.At present,the research on the interspecific soil moisture competition of the apple-crop intercropping systems only focuses on the description of phenomena,and lacks in-depth research on interspecific soil moisture competition mechanism and management technology.Therefore,in order to maximize the functions and benefits of the apple-crop intercropping systems,research on the competition status,competition mechanism and management techniques of apple trees and crops for soil moisture of the apple-crop intercropping systems,and provide a theoretical basis for the scientific management of efficient,stable and high-yield of the apple-crop intercropping systems.This paper takes the typical apple-soybean intercropping system and apple-peanut intercropping system on the Loess Plateau of western Shanxi Province as the research object,the monocropped apple trees,monocropped soybean and monocropped peanut as a control,and analyzes the spatial and temporal distribution characteristics of soil moisture and soil moisture effect of the apple-crop intercropping systems,and to analyze the interspecific soil moisture competition of the apple-crop intercropping systems.To study the fine root spatial distribution,fine root distribution variation,the relationship between the total fine root amount and soil moisture of the apple-crop intercropping systems,and to explore the competition mechanism of apple trees and crops for soil moisture of the apple-crop intercropping systems,and to quantify the interspecific soil moisture competition of the intercropping systems,and propose the field management and control measures to alleviate the interspecific soil moisture competition of the intercropping systems.The effects of proposed management measures on the growth characteristic,yield and water use efficiency of apple trees and crops were studied,and screen out measures that can effectively alleviate interspecific soil moisture competition of the apple-crop intercropping systems and improve the productivity of the systems.The aim is to minimize interspecific soil moisture competition of the apple-crop intercropping systems,and to maximize the utilization of moisture resources,which provides an important theoretical and decision-making basis for the study of system regulation and management techniques of apple-crop intercropping systems in the region.Research indicates:(1)Temporal and spatial distribution characteristics of soil moisture and soil moisture effect of the apple-crop intercropping systems:the soil moisture status of the apple-peanut intercropping system was better than that of the apple-soybean intercropping system.The soil water content of apple-soybean and apple-peanut intercropping system decreased with the increased of intercropping apple tree age,and increased with the distance from apple trees row increased,and increased with the increased of soil depth.The soil moisture content of the intercropping systems was smaller than the corresponding monocropped apple trees and monocropped crops in each soil depth.The soil moisture effect of the apple-crop intercropping systems:the negative effect of soil moisture in apple-soybean intercropping system was larger than that of the apple-peanut intercropping system.The apple-soybean and apple-peanut intercropping system had the largest soil moisture negative effect during the flowering stage-podding stage of the crop,followed by the podding stage-mature stage and seedling stage-flowering stage;the negative effects of soil moisture in the two cropping systems were increased with the increased of intercropping apple tree age,and decreased with the distance from apple trees row increased,and decreased with the increased of soil depth.The main competition areas of apple trees and crops for soil moisture in the apple-crop intercropping systems of intercropped apple trees at 3,5 and 7 years old were within the range of 0.9m,1.3m and 1.7m from the apple tree row.(2)Fine root characteristics of apple-crop intercropping systems and competition and utilization of soil moisture:in horizontal direction,with the distance from the apple tree row increased,the fine roots of the apple trees gradually decreased,while the fine roots of the crops gradually increased.In vertical direction,the fine roots of apple trees increased first and then decreased with the soil depth increased,and the soil layers of 20-40 cm were the most distributed,and they were concentrated in the depth of 0-60 cm soil depth.The fine roots of the crops decreased with the the soil depth increased,and were mainly concentrated in the depth of 0-20 cm soil depth.The distribution variation of fine roots:the fine root vertical barycenter of intercropped apple trees were deeper than that of monocropped apple trees,while the fine-root vertical barycenter of intercropped crops were shallower than that of monocropped crops;the fine root vertical barycenter of intercropped apple trees and intercropped crops moved to deeper soil with the distance from apple tree row increased.The relationship between total fine roots and soil moisture:the total fine root biomass density of the apple-soybean and apple-peanut intercropping system was negatively correlated with soil water content in both horizontal and vertical directions(P<0.01).The interspecific soil moisture competition index:the interspecific soil moisture competition intensity of the apple-soybean intercropping system was greater than that of the apple-peanut intercropping system,and both of them increased with the increased of intercropping apple tree age,and decreased with the distance from apple trees row increased.The interspecific soil moisture competition intensity index of apple-crop intercropping systems with apple tree age of 3,5 and 7 years was larger in the areas of 0.5-0.9m,0.5-1.3m,and 0.5-1.7m from apple tree row,respectively;and all of them were greater than 0.5.(3)Field management measures and soil moisture regulation and control of the apple-crop intercropping systems:the straw mulching and film mulching measures were applied to the apple-soybean and apple-peanut intercropping systems,respectively.And the fierce competition area on the south side of the tree row,the central competition area and the fierce competition area on the north side of the tree row were irrigated,respectively.And the lower irrigation limits of the crops at the seedling stage-flowering stage,flowering stage-podding stage and podding stage-mature stage of crops were set to 55%,85%and 70%of the field water holding capacity,respectively.These measures had a certain gain effect on the relative content of chlorophyll and the growth of new shoots of apple trees,and help to alleviated the interspecific soil moisture competition of the apple-crop intercropping systems,and improve the yield and water use efficiency of soybeans and peanuts. |
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