Effects of Split Application of Fertilizaer and Planting Density on Yield, Components of Yield, and Other Agronomic Characters of Rice (III)

Abstract

The rice variety, Chianung 242 was subjected to 4 levels of fertilization and two levels of planting density arranged in a 4×2 factorial oxperiment with four replications. The experiment was conducted at Chiayi Agricultural Experiment Station in the first crop of 1964. Data on grain yield, components of yield and several other agronomic characters were taken to analyze the effects of the treatments as well as their interactions. Split fertilizaions generally produced higher yields than conventional one, a difference exceeded the 5% level of probability. The yield increase appeared to be due largely to the increase of panicles and grains. Responses of grain yield as well as other agronomic characters measured to the split application of phosphoric fertilizer were not evident. However, there were indications for the effects of split applications of nitrogen and potash fertilizers. Splitting nitrogen four times with the ratio of 3: 3: 3: 1 during the entire period of growth gave, so far, the highest grain yield. Higher dosages of nitrogen applied at the first top-and second top-dressings resulted in the decrease of grain yield, severe occurrence of neck blast disease and lodging, suggesting that splitting ratio of 6: 3: 3 was better than that of 2: 4: 4 under the conditions of this experiment. For potash fertilizer, the splitting ratio of 6:4 gave better grain yield than that of 6.7: 3.3. Applying first top-, second top-, and third top-dressings at stages of maximum tillering, floral primordia differentiation and spiklet and pollen mother cell differentiations, respectively, appeared to be effective. However, other alternatives should also be explored. The high planting density produced higher yield than lower one, a difference exceeded 1% level of probability. The yield increase was attributable to the increase of panicles per unit area. Rice plants in the plots of split fertilizations generally tillered less with shorter culms in the early stage of growth, but they overgrew those of conventional fertilization for these characters at the maturing stage. The panicles of split fertilizations were generally heavier and longer than those of coventional one. Number of tillers, plant height, panicle weight and panicle length were generally decreased in the plots of high planting density. Split fertilzations significantly stimulated the occurrence of neck blast disease which, in turn, caused a reduction in grain weight. Planting density did not affect the occurrence of rice blast disease. Split fertilizations significantly increased the length of internodes especially that of the third and the fifth internodes. The elongation of internodes, especially at the third and the fifth, seemed to be related to the severe lodging of the plots treated with split fertilizations. The results suggested that the practice of split fertilization in the first crop should take into account the occurrence of blast disease and lodging. Planting density did not cause a significant change in the length of internodes. However, there was tendency for a high planting density to accompany a higher percentage of lodging. There were no significant interactions between the split application of fertilizers and planting density for all the characters measured in this experiment.