Agronomic studies on regional difference in growth and yield of rice in the Honam Area., 1; The effect of planting densities and transplanting dates on growth and yield in rice plant

This study was carried out to examine the effects of transplanting date and planting density on the yield and yield components with two rice varieties; Dongjinbyeo and Pungsanbyeo. Rice plant was transplanted at three dates; May 20, June 5 and June 20 with two planting densities at two locations; 22.2 and 30.3 hills in Iri, 25.6 and 30.3 hills per m** (2) in Kwangsan. During rice growing period, mean temperature was higher in Kwangsan than in Iri, but diurnal range of temperature and sunshine hours were reversed. The respiratory consumption effect of climatic condition was higher in Kwangsan than in Iri, being greatest difference at reproductive growth stage. Effective tillering ratio was lower in Kwangsan than in Iri, and increased by delaying the transplanting date and decreased by dense planting. Leaf area index and dry matter weight at heading stage was less in Kwangsan than in Iri and increased by dense planting in both locations. Kwangsan showed higher Crop Growth Rate (CGR) than in Iri at early growth stage, but lower at heading stage and after that, CGR droped markedly. CGR was showed the highest from panicle formation stage to heading stage in Iri, from maximum tillering stage to panicle formation stage in Kwangsan. Harvest index was higher in Iri than in Kwangsan and it was increased by dense planting except for the case of Pungsanbyeo in Kwangsan. Absorbed amount of nitrogen and phosphorous at heading stage was higher in Iri than in Kwangsan. Number of panicles per m** (2) in Iri showed high by 56 compared to in Kwangsan, it was increased by 63 in Iri, by 27 in Kwangsan by dense planting. Number of spikelets per plant in Kwangsan was lower by 7 than in Iri. Filled grain ratio did not show significant difference betweeen two locations. Yield per 10a was lower in Kwangsan than in Iri, and increased by dense planting in both locations