Growth and Yield Performance of the Water Chestnut(Trapa bispinosa Roxb.). I. Relationship among yield, yield components and change of number of rosettes.

Abstract

The yield performance of water chestnut plants cultivated in paddy fields under conditions of varying combinations of time and density of transplanting was investigated with reference to the change of number of rosettes. Yield was measured using the fresh weight of commercially valuable fruits, which weighed more than 10 g each, and was analyzed as the product of average weight per valuable fruit and their number per unit area. The latter, furthermore, was analyzed as the product of the number of productive rosettes per unit area and that of valuable fruits on a rosette. After transplanting, the number of rosettes increased to the maximum rosette number stage with the emergence of the branch stem, and after that decreased slightly, and then approached the final number of productive rosettes. By early transplanting and high density of transplanting, the increase rate of rosettes per unit area was enhanced and the maximum rosette number stage was hastened. As a result, the final number of productive rosettes per unit area increased. Yield varied from 780 gm-2 to 1140 gm-2 with treatment. High yield was obtained by early transplanting and high density of transplanting. Since the average fresh weight of valuable fruits did not vary by treatment, yield was mainly influenced by the number of valuable fruits per unit area. Judging from the small change seen in the number of valuable fruits on a rosette, the number of valuable fruits unit area varied in accordance with the number of productive rosettes per unit area. Therefore, the number of productive rosettes per unit area showed the closest correlation with yield among yield components. Consequently, the increase rate in the number of rosettes before the maximum rosette number stage was regarded as the important factor in greatly effecting yields.