Effects of Planting Density on Yield Components of Rice

Abstract

Experimental results of two rice varieties, Chianung 242 and Chianan 8, planted at two spacing treatments in the first crop of 1964 at Chiayi Agricultural Experiment Station are reported. Grain yield per hill decreased with increased population density, with Chianan 8 decreasing at a higher rate than Chianung 242. However, per unit area grain yield increased in Chianung 242, while that of Chianan 8 decreased at higher population density. A similar trend prevailed also in number of panicles per hill. Number of grains per panicle decreased whereas 100-grain weight increased at higher population density. The relationships among the 3 variables changed with spacing. Number of panicles per hill was positively associated with grain yield per hill, the correlation coefficients being highly significant. The magnitude of the correlation coefficients was reduced in Chianan 8 but increased in Chianung 242 with increased population density. Number of panicles per hill showed higher negative correlations with number of grains per panicle and 100-grain weight at high population density. Number of grains per panicle was also positively correlated with grain yield per hill. Weight of 100 grains was not significantly associated with grain yield per hill. Examination of the direct influence of yield components on grain yield per hill indicated that the number of panicles per hill was the most important character affecting grain yield per hill, and the number of grains per panicle ranked next. Weight of 100 grains had little direct influence on grain yield per hill. Residual factor appeared to have affected about 12 to 55% of the variation in grain yield per hill.