Preventoin of Lodging by Mixed Planting of Rice Varieties : I. Effects of alternate row-planting on loding and yield

[摘要] The effects of mixed planting on lodging and yield were examined at different nitrogen levels with direct sowing on well drained paddy field and with transplanting. Two cultivars 'Koshihikari', good tasting but tall and lodging-susceptible, and 'Kanto 100', short-startured and lodging-resistant, were used. Both of them are of the same maturity. Koshihikari and Kanto 100 were planted alternately to four rows and two rows, or two and two, or one and one, respectively. Results of the experiment can be summarized as follows: 1. The lodging of Koshihikari was clearly reduced by mixed planting. About 60% of the reduction was contributed by the propping effect of Kanto 100, and about 40% by the increase in lodging resistance of Koshihikari due to mixed planting. The number of photosynthetic leaves and leaf-sheaths, the stem diameter and the breaking strength of lower internode of Koshihikari in the mixed stand were increased than those in the pure stand. 2. Mixed planting increased the yield. The yield of Koshihikari obviously increased in mixtures and that of Kanto 100 tended to decrease. However, the yield increase in Koshihikari could abundantly compensate for the yield decrease in Kanto 100. On an average, the yield of the mixed stand increased by 6.7% more than the mean yield of the pure stands of the two cultivars. 3. The competition effects of varietal mixtures on the yield were analysed by setting up the artificial condition of no lodging through stretching a net for prevention of lodging. The yield increase in Koshihikari was nearly equal to the yield reduction in Kanto 100, therefore, the yield in the whole conlmunity did not increase. These results demonstrate that the yield increase by mixed planting without a net resulted mainly from prevention of lodging of Koshihikari, and this corresponded to about 60% of the yield increase in Koshihikari grown in the mixed stand, and that the remainder, about 40% of the yield increase in Koshihikari, was due to the competition compensating for the yield reduction in Kanto 100.

[学科分类] 农业科学（综合）