Status and changes of the properties of cultivated soil during a period of fifteen years in Chiba prefecture [Japan]
1998
Anzai, T. (Chiba-ken. Agricultural Experiment Station (Japan)) | Shinoda, M. | Yamaki, A. | Tobe, O. | Arihara, K. | Watanabe, H.
To analyze the status and changes of physical and chemical properties of soils cultivated over a fifteen year period, we carried out three soil surveys in the same fields. The first survey covered the period from 1979 to 1983 the second the period from 1984 to 1988 and the third the period from 1989 to 1993 after a five-year interval. This soil survey was designated as Basic Survey for Soil Environment. The results obtained were as follows: 1) Paddy fields: The depth of the plowed soil layer which was 12.7 centimeters decreased remarkably in the last 5-year period. The pH (H2O) decreased, the contents of total carbon, exchangeable calcium and magnesium decreased while the content of available nitrogen increased. These results suggested that most of the paddy fields tended to become well-drained, although the proportion of paddy fields that became ill-drained also increased. 2) Upland fields under common crops: The pH (H2O) decreased, the contents of available nitrogen and phosphate, exchangeable calcium, magnesium and potassium and nitrate nitrogen decreased. However, the values of these elements tended to imrove, abased on the soil diagnosis standards. 3) Upland fields under vegetables: the depth of the plowed soil layer, the contents of exchangeable calcium and magnesium increased while the contents of available phosphate and exchangeable potassium decreased or remained unchanged during the last 10-year period. The accumulation of the latter two elements in soil decreased. 4) Upland fields under forage crops: among the physical properties, depth of the plowed soil layer, bulk density, compactness and ratio of the solid phase increased, while among the chemical properties, pH(H2O), contents of a valuable nitrogen and phosphate and exchangeable potassium also increased with the passage of time, respectively
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