Effects of intercropping soybeans with different root architecture and sweet maize on crop growth and phosphorus uptake
[Objective]To study the effects of intercropping soybeans with different root architecture and sweet maize on crop phosphorus(P)uptake and growth under different P levels,and explore the relationship among root morphology,root architecture,P availability in rhizospheric soil and so on within the intercropping system.[Method]Field experiments were conducted in August 2022 at the Teaching and Experimental Base of South China Agricultural University in Zengcheng District,Guangzhou City,Guangdong Province.Two different soybean cultivars,namely'Bendi 2'(deep-rooted genotype)and'Yuechun 03-3'(shallow-rooted genotype)were selected as experimental materials.The field experiment employed a split-plot design,with the main plots comprising two P application levels:With P(+P:40 kg·hm-2 for soybean,120 kg·hm-2 for sweet maize)and without P(-P:0 kg·hm-2 for both soybean and sweet maize).The subplots consisted of five different planting patterns as follows:Sweet maize monocropping,soybean'Bendi 2'‖ sweet maize,soybean'Yuechun 03-3'‖ sweet maize,soybean'Bendi 2'monocropping and soybean'Yuechun 03-3'monocropping.The yield,biomass,P uptake,root morphology and architecture of sweet maize and soybean were measured,and the land equivalent ratio(LER)and interspecific competitiveness of the intercropping system were calculated.[Result]Intercropping soybean significantly increased the yield of sweet maize by average of 33.4%under both P levels.Under-P condition,intercropping soybean significantly increased the biomass of sweet maize by average of 62.7%.Intercropping sweet maize and soybean exhibited advantages,influencing by P application levels.Under+P condition,the average LER for intercropped sweet maize and soybean was 1.08,while under-P condition,the average LER increased to 1.21.Interspecific competition analysis indicated that in the intercropping system,sweet maize showed significantly stronger competitiveness than soybean(interspecitic competitiveness>0).This competitive advantage was more pronounced under-P condition.In addition,intercropping with deep-rooted soybean genotype('Bendi 2')significantly promoted P uptake in sweet maize under-P condition by average of 40.6%.Further analysis revealed that for deep-rooted soybean'Bendi 2',intercropping with sweet maize under-P condition widened its root width,altered the proportion of fine roots(diameter≤0.5 mm),and significantly increased P availability in the rhizosphere of intercropping maize.The correlation analysis of traits of soybean and sweet maize in the intercropping system revealed a significant positive correlation between the biomass of sweet maize and its total root length,root width of soybean,and available P content in the soybean rhizosphere soil.The biomass of soybean showed a significant positive correlation with its P uptake,total root length,root width,and available P content in the rhizosphere soil.However,it exhibited a significant negative correlation with its proportion of fine roots(diameter≤0.5 mm).[Conclusion]Intercropping with deep rooting soybean under-P condition can effectively promote the growth and P absorption of sweet maize,and increase its yield.These findings provide important theoretical basis for fully exploring the P utilization potential in the sweet maize‖soybean intercropping system,screening suitable soybean varieties for crop intercropping,and achieving reduced P fertilization rate with increased P use efficiency.
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