水稲品種の混作による倒伏防止に関する研究 : 第3報 組合せ品種の草丈差と倒伏防止効果および品種間競争との関係

抄録

(Experiment 1) The effects of mixed sowing on lodging and yield were examined when eight cultivars, having lodging-resistance and different plant length, were mixed with Koshihikari, which is tall and lodging-susceptible. Koshihikari and another variety were sowed alternately to two rows and two rows respectively. (Experiment 2) The relationship between intervarietal competition and difference of plant length was investigated, using twelve pairs of varieties which have different plant length, lodging-resistance and maturity. The method of mixture was the same with experiment 1. Both the experiments were carried out with direct sowing on well drained paddy field. Results of the two experiments can be summarized as follows : 1. It was recognized that all the varieties used in experiment 1 brought the positive effects of mixed sowing on lodging reduction and yield increase for Koshihikari. The shorter plant length of variety, the more effect on lodging prevention was observed. And the significant correlation coefficient was obtained between them. 2. Tall varieties showed greater competitive ability than short varieties. This suggests that the competitive ability is due mainly to the plant length under the method of mixture used in these experiments. 3. The more difference of plant length between varieties, the greater competition was observed. Positive correlation coefficient was found between the difference of plant length and the change in yield by mixed sowing (per cent mixed hill yield / pure hill yield). In addition, a severe lodging increased competition, although the difference of plant length was little. 4. The yield in the mixed stand was significantly more than the average yield for the components grown in pure stand, but was not significantly more than that of the better of its components.