Abstract
Kenaf (Hibiscus cannabinus L.) is a potential alternative forage crop. The objective of this study was to examine the effect of cutting height on the yield in kenaf, cv. ‘Everglades 41’ harvested two times in a single growing season under upland and lowland field conditions. In Exp. 1, to clarify the optimum cutting height at the 1st cutting, we cut kenaf plants at a height of 15, 20, 25, 30 and 35 cm, and measured fresh and dry weights of the 1st-cut and the regrowth of the cut plants in pot experiments. In Exp. 2, kenaf plants grown under paddy field conditions were cut at a height of 25 cm in 2006, and 20 cm in 2007; while the plants grown in the upland field, were cut at a height of 20, 25 and 30 cm in both 2006 and 2007. In Exp. 1, no significant differences in the sum of the aboveground yield in the 1st cutting and regrowth plants among the different cutting heights. However, the yield of the plants cut at 25 and 30 cm tended to be higher than that of the plants cut at other heights. In Exp. 2, the regrowth rates after the 1st cutting in the upland field were extremely low (3.0∼3.7%), and some irrigation water was needed after cutting at lower than 30 cm. Under the paddy field condition, however, although kenaf seedlings were transplanted to a water-logged paddy field with water at about 5cm depth of water, kenaf plants showed a regrowth rate of 100% and 97.4% in 2006 and 2007, respectively; and, they had a higher crude protein content. In addition, the low precipitation in summer did not severely affect the growth of kenaf in paddy fields differing from that in the upland field. Therefore it was estimated that kenaf could be produced as forage by harvesting two times a year in the paddy field.
