Effects of Placing Rice Straw, Wheat Straw and Rice Husks in Soil Ridges on Growth, Morphological Characteristics and Yield of Sweetpotato in Wet Lowlands.

Abstract

A concept of the hydroponic technique was applied to sweetpotato cultivation under field conditions in a wet lowland. Three easily available indigenous materials, rice straw, wheat straw and rice husks, were placed in soil ridges to make sufficient aerial spaces in the soil for better tuberous root development. The materials were used either unmixed with soil (the Mass treatment) or mixed with soil (the Mixture treatment). Water depth between the ridges was kept at 20mm throughout the growing period in order to imitate the wet soil conditions in tropical and subtropical lowlands. The growth characteristics and yield of sweetpotato grown in the Mass and Mixture treatments were compared with those grown in a conventional control. The fresh and dry weights of the total phytomass per plant were greatest with the Mass treatment using rice husks. The fresh and dry weights of above-ground parts in the Mass treatments were approximately 0.7 times those in the control. On the other hand, the fresh and dry weights of sub-ground parts in the Mass treatment using rice husks was 4.1 times greater than those in the control. The Mass treatment using rice husks gave 5.8 times greater fresh and dry weights of tuberous roots than in the control. The edible biomass (tuberous roots) index obtained with the Mass treatment using rice husks (61.4%) was 4.4 times that in the control.