Effect of Soil Moisture Content on Growth and Yield of Azuki-beans, Phaseolus radiatus var. aurea PRAIN : I. Growth and yield as affected by the different soil moisture content : II. Varietal differences of growth and yield at different subirrigated water levels

Abstract

1) Optimum soil moisture content for growth and yield of Azuki-beans was investigated on the different soils, several sowing dates and the some varieties. 2) Even under the same condition of soil and water content in pot culture, the different structure and the amounts of soil produced somewhat different results on the growth of this crop. 3) The optimum soil moisture content for the growth :and yield of Azuki-beans were 90∼80 % of water capacity and the moisture range for practical .growing of this crop was about l00∼60 %. The growth and yield of this crop grown under 40 % moisture content showed marked depression. 4) In this treatment, the root-top ratio showed the minimum and maximum value under optimum and the least soil moisture content, respectively and transpiration ratio under optimum conditions was more than 400. 5) During the early stages of growth soil moisture content required for the normal growth was comparatively low and in this period the plant growth was considerably normal even under dry condition as low as 40 %. Until about 40 days after sowing, the growth of this crop had not shown any appreciable differences by the different soil moisture treatments from 60 to 100 percent. Thereafter, growth rate was effected largely by the, different soil moisture content. 6) 4 varieties, early to late, were cultivated in the soil shelves .having the height of 10, 30, 50, 70, 90 cm from the constant level of subirrigated water table. 7)The soil was coarse sandy loam well aggregated to have good aeration. Soil moisture content of each layer of all plots was measured. (Fig. 2). 8) Plant height, number of nodes, condition of branching, dry weight of a plant increased according with lower and wetter conditions except 10 cm -high plot, this trend being more remarkable on the early rather than the late variety. 9) The early variety bloomed few days earlier in high level plots than low level plots, but the late did not show such a, difference. Number of pods, total number and weight of fertile grains increased with the lower and wetter conditions especially in the case of early variety, except 10 cm high. Weight of 100 grains of the early varieties increased but that of the late variety decreased with increasing soil moisture. The reason why the yield of the late varieties did not increased in spite of the increase of the total number of fertile grains as compared with the early varieties was the increase of the refuse grains. 10) In this study, the suitable height from the subirrigated water level for their growth and yield was estimated to be 30 cm in the early varieties and 50∼70 cm in the late varieties.