Effects of plant density on the performance of selected African upland rice varieties

Abstract

The effects of plant density on yield and yield components in upland rice cultivation were examined by conducting a series of field experiments in Central Uganda, using three African and one Japanese improved upland rice varieties. The estimation of plant-density response functions with respect to yield components and yield revealed that an increase in plant density significantly decreased the number of panicles per hill, number of spikelets per panicle, and 1000-grain weight, and significantly increased the number of panicles per square meter. The percentage of filled grain was not affected by plant density. Compared to the Japanese variety, the three African varieties were characterized by more numbers of panicles/hill, less numbers of spikelets/panicle, higher grain-filling ratio and lighter 1000-grain weight, but differences in the degrees of response to plant density were less distinct between them. Rice yield increased in the range of plant density tested, though the marginal increase in yield due to an increase in plant density by 1 hill/m 2 diminished from 100 kg/ha at the plant density of 11 hills/m 2 to 30 kg/ha at 33 hills/m 2 . No significant differences were found among the four varieties for the level of yield as well as for its degree of positive response to plant density. The yield components that determined the increase in yield were the number of panicles per square meter and the number of spikelets per panicle, or combined together, the number of spikelets per square meter, which was estimated to reach the maximum at the plant density of 35 hills/m 2 . When the differences among the treatments in the costs of seeds and weed-control were considered, the optimum plant density was found to be 22 hills/m 2 (plantspacing of 30 cm × 15 cm), lower than the plant density that gives the maximum yield.

Effect of Plant Spacing on the Growth and Yield of Rainfed Rice (Oryza Sativa) in the Bimodal Rain Forest Zone of Cameroon

“…There was no significant difference in the weight of 1000 seeds and the percentage of full seeds for both varieties for all spacing, whereas the differences were highly significant for the number of tillers per m 2 and significant for the number of grains per panicle. These results agree with those of Shunsuke, et al [7] who found that the weight of 1000 grains was not significantly different for different spacing. Other authors such as Clerget, et al [14], Hayashi, et al [15] and Nakano, et al [16] did not find similar results on the effect of plant density on the yield components.…”

“…The results reveal that there was no significant difference for weight of 1000 grains for the two genotypes and across the years. These results match with those of Shunsuke, et al [7].…”

“…The plants from the large spacing were tall with long panicles. Similar results were obtained by Shunsuke, et al [7].…”

“…Rice is a relatively new crop, exotic and unfamiliar for upland farmers in many parts of Africa. The optimal plant density in plateau rice production and crop management is an example of such challenges [7].…”