Hayashi's theory of quantification No.1 was used to examine the contribution of environment, soil, and management factors to crop yield in Nagasaki prefecture. The yields of paddy-rice, potato, and orange were considered. All the data employed in the quantification analyses were collected from the Dojo-kankyo-kiso-chosa (soil survey for improved utilization and conservation of soil resources) which was carried out as a national project from 1979 to 1987. The yield of paddy-rice was closely related to the items used in the study. Among the items, the most important item to control the paddy-rice yield was the environmental items of weather and physiography. Soil type (soil series) was well related to the averaged yield of paddy-rice under the same physiographic unit. The contribution of rice variety and rate of nitrogen fertilizer application to the yield was low compared with the contribution of soil type. Soil chemical properties hardly affected the paddy-rice yield. The correlation between the yield of potato and items was not so good. Items relating to environment less contributed to the yield than items relating to soil and management did. Among the items used, soil type, soil chemical property, and rate of nitrogen fertilizer application were important to control the potato yield. The yield of orange showed the higher correlation to the environmental items than to the soil and management items. The averaged yield of orange was well related to the physiographical environment, although the contribution of weather was not clear. The effect of soil chemical property on the orange yield was greater than the effect of rate of fertilizer and lime application. The phosphate-absorption coefficient of a soil may be a good index to the potential productivity classification of orange field consisting of Red-Yellow soils.
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