Improvement of paddy soil derived from glassy volcanic ash (shirasu) by successive applications of organic and inorganic amendments
1994
Kamimura, Y. (Kagoshima-ken. Agricultural Experiment Station (Japan)) | Furue, K. | Nishizono, N.
A field experiment has been carried out since 1975, in order to maintain a high yield of rice cultivated in a paddy soil derived from glassy volcanic ash (Shirasu) which has potentially low productivity. In this experiment, farmyard manure or rice straw was applied as organic amendment, and slag and calcium silicate as inorganic amendments. The response of rice yield to the organic treatments was resulted of a large quantity of grains per panicle in the plots supplemented with farmyard manure, while by a high percentage of ripened grains in the plots treated with rice straw. The percentage of ripened grains in the organically treated plots, however, was lower than the plots treated with chemical fertilizer. The total carbon and nitrogen contents of the soils increased through successive applications of organic matter, resulting in a high carbon-nitrogen ratio. The amount of available phosphorus measured by the Truog and Bray No.2 methods also increased through the application of farmyard manure. Organic components of soils such as cellulose increased by the organic treatments. The lignin content of the plots treated with farmyard manure also increased. The increase of rice yield did not exceed 10% in the organic plots compared with the chemical fertilizer plot, in spite of the increase in nutrient-uptake by rice plants through successive applications of organic amendments. Therefore, some suggested that the methods of fertilizer application should be improved to further increase rice yield in paddy soils derived from glassy volcanic ash (Shirasu)
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