Identification and Evaluation of Toxicity of Rice Root Elongation Inhibitors in Flooded Soils with Added Wheat Straw

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We studied the growth and chemical composition of Miscanthus sinensis in various locations showing significant differences in climate, elevation, and properties of Andisols in northeastern Japan. Accumulated effective temperature above 10℃ (AET) was found to be a very useful index to analze the relationships between climate and plant growth such as plant height, leaf number, and dry matter production. M. sinensis ecosystems occurring at the upper limits showed almost the same minimum leaf number (12-13) and AET (26-29) in all the study areas. The plant produced large amounts of organic matter not only in the aboveground part but also in the underground part. The contents of plant mineral constituents were determined during the growing season. No minerals except Al showed variations in content depending on yearly changes in climate and differences in soil conditions. The mineral uptake per unit area was large for K and Si, medium for N, low for P, Ca, and Mg, and very low for Al. Finally we discussed the significance of M. sinensis as andisolizor in focusing on the correspondence of the upper limit of the M. sinensis ecosystem with that of the distribution of very dark-colored Andisols, input of a large amount of organic matter by the ecosystem to the soils for a long period of time, and mineral cycles between the ecosystem and soils.