Characteristics of soil that flowed into paddy [Oryza sativa] fields by the Fukui [Japan] heavy rain
2006
Kanda, M.(Fukui-ken. Agricultural Experiment Station (Japan)) | Imori, H. | Miyashita, T. | Nogami, M. | Kodani, Y. | Mizusawa, Y.
Heavy rain that occurred in Fukui Prefecture on July 18, 2004, caused extensive damage. Soil flowed into a number of paddy fields. Therefore, we investigated and analyzed the deposited soil for cultivation. 1. Particle size analysis revealed that the rate of sand deposition increased as the river became more upstream and the deposited soil near from the river. However at the upper Asuwa River, a high rate of clay and silt accumulated by the influence of landform. 2. The deposited soil was high CEC and excellent nutrient retention. The pH was high, because of the presence of a considerable amount of exchangeable calcium and magnesium. Since the soil contained exchangeable potassium and available phosphorus as well as a considerable amount of available nitrogen, it is considered that the fertile soil entered the paddy field. However a considerable amount of easily reducible manganese decomposed and flowed out of the parent material was also accumulates and superfluous at almost all the investigation point. Therefore, in order to achieve a low manganese level, when growing crops, it is necessary to thoroughly mix the conventional plow layer under the deposited soil. 3. The amount of available nitrogen also increased, resulting in a high viscosity of the deposited soil. In comparison with the topsoil before the flood damage, there was a considerable amount of available nitrogen even though the total nitrogen and humus content in the deposited soil was low. This is because organic matter in the deposited soil is easily decomposable, and thus nitrogen mineralizes easily.
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