Abstract
Rockwool was placed in soil ridges in order to create sufficient aerial spaces in soil for better tuberous root development of sweetpotato. The rockwool was either mixed (the Mixture treatment) or not mixed with soil (the Mass treatment). The water depth between the ridges was kept at 20 mm throughout the growing period in order to imitate the wet soil conditions in lowlands. The growth characteristics and yield of sweetpotato grown in the Mixture and Mass treatments were compared with those grown in a conventional control. The fresh and dry weights of the total phytomass per plant were greater in the Mixture and Mass treatments than in the control. The fresh and dry weights of the sub-ground parts in the Mixture treatment were 2.1 and 2.4 times greater, respectively, than those in the control. Higher fresh and dry weights of the tuberous roots were obtained in the Mixture treatment. The Mixture treatment showed approximately 3 and 2 times greater, respectively, fresh and dry weights of the tuberous roots than in the control. The maximum tuberous root diameter in the Mixture and Mass treatments were 1.5 and 1.3 times greater, respectively, than that in the control. The shoot/root ratio was lower in the Mixture treatment followed by the Mass treatment and a higher shoot/root ratio was obtained in the control. A higher edible biomass index was obtained in the Mixture treatment followed by the Mass treatment and was the lower in the control.
