| Rational intercropping cultivation can make full use of the spatial structure principle of the community and improve the crop’s utilisation of resources such as light,temperature,water,air,fertiliser,time and space.Exploring the effects of different soybean width variations on the maize-soybean intercropping system and on water and nutrient utilisation is conducive to finding suitable soybean widths for the promotion of production applications.Intercropping between grasses and legumes can improve the uptake and transformation of soil nitrogen by crops and enhance the productivity advantage of intercropping,but the crop nitrogen change patterns and interspecific relationships are unclear for the maize and soybean intercropping system in the Ningxia Yellow Irrigation Area.In this study,a field trial of maize and soybean intercropping was conducted in 2021 in Xihe Village,Yongning County,Yinchuan City,Ningxia Province,using a one-way randomized group design with five treatments:maize monoculture,soybean monoculture,maize intercropped with soybean(soybean width 60 cm),maize intercropped with soybean(soybean width 80 cm)and maize intercropped with soybean(soybean width 120 cm).The experiment investigated the changes of soil moisture,nitrogen and biomass under the maize and soybean intercropping system;analysed the distribution and uptake of nitrogen in various organs of the plant,the accumulation of above-ground dry matter,crop yield and interspecific relationships;and also explored the effects of intercropping on the soil microbial community.The main findings of the study are as follows.(1)The intercropping of maize and soybean promoted the uptake of soil total N,nitrate N,ammonium N,total phosphorus,fast-acting phosphorus and fast-acting potassium by the crop;Intercropping treatments with different soybean widths reduced soil water content;the water demand of the intercropped crop was greater than that of the monocropping treatment,and the stable isotopes of soil water δD,δ17O and δ18O were significantly enriched in the 0-10 cm soil layer under different treatments.(2)Intercropping of maize and soybean had no significant effect on soil microbial biomass carbon;soil microbial biomass characterised by PLFAs was higher in the intercropping pattern than in maize alone,and the biomass of all microbial groups showed that bacteria>actinomycetes>fungi,while the biomass of Gram-negative bacteria was greater than that of Gram-positive bacteria in the bacterial composition,and the total soil microbial biomass showed that the intercropping treatment with soybean width of 60 cm>soybean accumulation>intercropping treatment with soybean width of 80 cm>maize accumulation>intercropping treatment with soybean width of 120 cm.(3)Intercropping between maize and soybean increased nitrogen uptake by the above-ground parts of maize.At maturity,nitrogen uptake by maize stems was 42.86%,21.43%and 54.76%higher in the soybean width 60 cm,80 cm and 120 cm treatments,respectively,than in maize accumulation;nitrogen content by maize seeds was 13.22%,13.22%and 10.34%higher than in maize accumulation.Significant differences in nitrogen uptake by aboveground stems,leaves and seeds of intercropped soybean were observed under different width intercropping treatments.At maturity,the nitrogen uptake of soybean leaves was 8.33%and 3.62%higher in the 60 cm and 120 cm soybean widths,respectively,than in monocropped soybean,and the total nitrogen content of soybean seeds was 7.41%,12.38%and 9.31%higher in the 60 cm,80 cm and 120 cm widths,respectively.(4)In the maize and soybean intercropping system,maize was the dominant crop and soybean was the inferior crop.The above-ground biomass of maize plants was higher than that of maize accumulation under the intercropping treatments of 60 cm and 120 cm width of soybean at the end of the intercropping period,while the opposite was true for soybean;under maize intercropping with soybean of different widths,the distribution ratio of maize ears was higher than that of maize accumulation,and the distribution ratio of pods in intercropped soybean was lower than that of soybean accumulation.(5)The yield land equivalent ratio under different soybean width intercropping cultivation patterns is less than 1,with no intercropping advantage;the relative interspecific competitiveness is less than 0,indicating that soybean is less competitive than maize for resources... |
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