抄録
In Japan, early growth injury of sorghum from continuous cropping has been observed, especially in andosols. Large-size plot field experiments demonstrated that early growth injury was more severe in andosols than in other soil types and that there are varietal differences in injury severity. The low phosphorus content of the injured plants was suggested to be related to the anthocyanin development of sorghum early growth injury. Potassium content in the early growth-injured plants in continuously sorghum-cultivated soils tended to decrease compared with those in sorghum-uncultivated soils. Other mineral contents of Ca, Mg, Fe, Mn, and Zn were not likely to be related to the development of sorghum early growth injury. The 121℃ autoclave-sterilization treatment of continuously sorghum-cultivated soil improved sorghum plant length and shoot dry weight compared with fresh soil treatment. Meanwhile, soybean plants were not affected by the fresh soil treatment of continuously sorghum-cultivated soil. The 80℃ steam sterilization of continuously sorghum-cultivated soil made the sorghum growth healthy, with the same level of growth in sorghum-uncultivated soil. This suggests that certain causal microbes can lead to sorghum early growth injury. Sorghum allelopathy may be related to early growth injury, but the findings of pot experiments suggested that the allelopathic influence would not be determinable as a causal agent. Certain microbes were observed on the root surfaces of the injured plants. We anticipate that further studies will clarify the possible causal microbes by fungal DNA sequencing analysis of young reddish roots grown in continuously sorghum-cultivated andosols.
