Studies of Direct-sowing Rice Culture by Broadcasting of Seed on submerged Paddy Field : IV. Relationship of seeding density to plant growth and rice yield

Abstract

Pot tests were attempted at Faculty of Agriculture, Okayama University in 1963 as to the relationship of seeding density to plant growth and rice yield in case where rice seed was sown by broadcasting by hand directly on the submerged paddy field. Size of each pot: 1 meter long, 0.8 meter in width, and 1 meter in depth. Sample rice variety: PI-5. Tests were made by four replications as to the seven plots (from 30-hill plot to 210-hill plot) aligned at random. Fertilizers were applied according to the customary practice. Test results can be summarized as follows : (1) At the earlier plant growth stage, culm height of rice plants in the densely sown plots was higher than that in the sparsely sown ones, but vice versa at the later plant growth stage. (2) At the peak tillering stage, the number of tillers per unit area in the densely sown plots showed an increase over that in the sparsely sown ones, but after that stage, the former showed a marked decrease in the number of tillers. At the harvesting time, the number of panicles in 90-hill plot was greatest, reaching 502 panicles per square meter and that in 30-hill plot was smallest, showing 304 panicles and that in the plot sown more densely showed a decrease to about 405 panicles. (3) Rice yield in 90-hill plot was highest. This is due to the greatest number of panicles therein. (4) Rice yield in the plots sown densely more than 120 hills was lower than that in 90-hill plot. This can be ascribed to the inadequate amount of the customary fertilizer application for the densely sown plots in the later plant growth stage. Consequently, if improved split-application practice be designed, rice yield in the densely sown plots would show more favorable trend than that in other plots.