Effect of Volume of Rice Husk Charcoal Masses inside Soil Ridges on Growth of Sweetpotato in a Wet Lowland

Abstract

We placed rice husk charcoal masses with different dimensions into soil ridges (500 mm in width and 250 mm in height) for promoting soil aeration in a wet lowland, and investigated sweetpotato growth and the soil gas component. The widths of the rice husk charcoal masses were 0 (control), 75, 150, 225 and 300 mm, and the thickness of each mass was 120 mm. The material was covered with 80 mm thick soil. Water depth between the ridges was kept at 20 mm throughout the growing period to maintain a wet soil condition. The dry weight of the total phytomass was greater in the 150 and 225 mm width treatments than in the other treatments. The dry weights of shoot and the tuberous roots in the 150 mm width treatment were 0.6 and 1.4 times, respectively, those in the control. The number, length and diameter of tuberous roots were greatest in the 150 mm width treatment. The carbon dioxide concentration in the soil ridge was almost double in the control compared with the 150, 225 and 300 mm width treatments. The lower carbon dioxide concentration in the soil ridges and an adequate soil volume for supplying water and nutrients to theroots would partly account for the better developmentof tuberous roots in the 150 and 225 mm width treatments. © 2000, The Society of Agricultural Meteorology of Japan. All rights reserved.