Studies on the Soy-Bean Cultivation on fields at Volcanogenous Diluvial Soils. : (I) Relationship between the seasonal fluctuation of soil moisture content in each soil layers and the growth and yield of soy-bean.

Abstract

Experiments were carried out, in 1950, 1951 and 1955, to elucidate the relations between the seasonal fluctuation of soil moisture content in each layers and the growth and yield of soy-bean, at Kanto-Tosan Agriculture Experiment Station, Ministry of agriculture and Forestry. Plants were grown on two fields, one being of alluvial soil and the other being of volcanogenous diluvial soil. The results obtained are summarized as follows; (1) On the field of volcanogenous diluvial soil, where the underground water level became deeper than 250 cm in summer season, the moisture content of soil layer to 60 cm depth was mainly influenced by precipitation. Particularly the water content of the upper portion of soil to 15 cm depth was entirely dominated by precipitation and consequently seasonal fluctuation of soil moisture content was very large in that portion, but at the depth of 30 cm, it became somewhat small, and at 45 and 60 cm, soil moisture content was abundant and fluctuation was very small. In the field of alluvial soil, where the underground water level was higher than 100 cm below the surface, the soil moisture content was generally abundant, and the seasonal fluctuation did not occurred at 40 cm depth. (2) In the early growing period, the growth of soy-bean was slightly better on the diluvial soil than on the alluvial soil, but afterwards as its growth proceeded, the plants on the diluvial soil became poorer and at harvesting time, they were somewhat inferior with regard to the culm-length and number of nodes. They were also very inferior in the culm-weight, 100 seed-weight and number of pods, and particularly their yield of seeds was low as about 60 % of that on the alluvial soil. The results may clearly explain the fact that soy-bean plants grown on diluvial soils were strongly affected by deficient soil moisture content during the period from blooming to ripening in 1951.