Optimum plant population of hybrid rice in single cropping
1989
Huang, P. | Miao, B. (Nanjing Agricultural Univ., Jiangsu (China))
The plant population, number of tillers, and leaf area index (LAI) required for the optimum number of panicles to give maximum filled spikelets per panicle for high yields of hybrid rice were determined in experiments conducted from 1977-1979. The optimum panicle number to achieve the highest filled spikelets percentage was 289 panicles/sq. m. The optimum number of spikelets per panicle was 179. The effect of plant population on panicle number, grain weight, and filled percentage is described. Panicle number per unit area is a function of leaf area. The leaf area of a single tiller of hybrid rice was 240-250 sq. cm at heading, about 50 sq. cm more than that of IR24, indicating that the capacity of IR24 for producing effective tillers is less than that of hybrid rice. Shan-You 2 yields highest at maximum LAI of 7.6 at heading. For Shan-You, Nan-You, etc., 3 million panicles/ha is the theoretical optimum. Filled spikelet percentage and grain weight are functions of net photosynthetic rate and dry matter accumulation. There is significant positive correlation between dry weight of stem and leaf sheath per spikelet and the percentage of filled spikelets (r=0.712**, DF=16). If LAI is 6.3-7.3 at heading, net photosynthetic rate remains higher during the 20 d after heading and dry matter accumulation is 3.8-5.7 t/ha.
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