Effect of Winter Crop Species on Arbuscular Mycorrhizal Fungal Colonization and Subsequent Soybean Yields

We evaluated how the cultivation of arbuscular mycorrhizal fungi (AMF) host (wheat) and non-host (rapeseed) crops affects the subsequent soybean crop by assessing AMF spore density and AMF colonization, phosphorus (P) uptake by soybean and yields of soybean over a 4-year period. Every year wheat or rapeseed was cultivated from autumn to spring and soybean from spring to autumn. From the first to fourth year, AMF spore density was higher in the plot after the cultivation of wheat (wheat plot) than in the rapeseed plot. From the second to fourth year, the AMF colonization ratio was higher in the wheat plot than in the rapeseed plot. In the first year, there was no difference in the AMF colonization ratio, growth, and P uptake by soybean plants between the rapeseed plot and wheat plot. However, from the second to fourth year, AMF colonization ratio, plant growth, and P uptake by soybean in the wheat plot were higher than those in the rapeseed plot. The soybean yields in both plots gradually decreased from the first to fourth year, but, in the second and the fourth year, soybean yields were higher in the wheat plot than in the rapeseed plot. Soybean yield was significantly correlated with the AMF colonization ratio, but not with AMF spore density. Therefore, we concluded that AMF colonization is not determined by AMF spore density alone, and other factors influence the AMF colonization in subsequent soybean plants. It is important to increase the AMF colonization ratio to increase soybean yield