Dry matter production and yield components of Chieng Phatthalung rice cultivar under differnt planting methods

Currently, wet sown rice is the most popular crop establishment method in the southern region of Thailand. This is because of the increasing labor costs and the lack of labor supply at the beginning of the growing season. Research on growth and develoment in rice, including its yield components, obtained from different planting methods may be useful for improving grain yield. The objectives of this experiment were to analyse the difference of above-ground dry matter production at various growing stages which influenced yield components in rice. Data received from this study is important to crop growth modelling for yild elaboration process in rice in the south of Thailand. An on-farm experiment in six farmers' fields was conducted during the wet season from September 1995 to February 1996. A rice cultivar, Chieng Phatthalung, was used in this study. At each farmer's field, two planting methods were employed: wet sown rice in one plot and transplanted rice in another plot. Plant density in wet sown rice was about 400 plants/square m and a hill spacing in transplanted rice was approximately16-20 hills/square m. Variations in the number of plants/hill and the hill spacing in each farmar' s fields depended on his individual practice. Rate of nitrogen fertilizer application was 75 kg N/ha. The experiment was a randomized complete block design by using each farmer's field as a block. The results indicated that above-ground dry matter in wet sown rice at the stem elongation stage was highly significant higher than that in transplanted rice at the 0.01 probability level. The higher above-ground dry matter was due to a greater culm number/square m and the absence of transplanting shock in wet sown rice. Above-ground dry matter at 50 percent flowering and at harvest maturity were nearly the same in both planting methods. An analysis on yield components showed that wet sown rice had a higher number of panicles/square m but had a lower number of spikelets/square m and number of grains/square m than that in transplanted rice at the 0.05 probability level. The percentage of filled grains and the average of grain weights were not different between the planting methods. There was a relationship between grain yield and number of grains/square m in both planting methods with the coefficients of determination greater than 0.95. However, grain yield in wet sown rice was highly significant lower than that in transplanted rice at the 0.01 probability level. A lower weight of above-ground dry matter in the stem which was found in wet sown rice was through reduced development in the number of spikelets/panicle. Therefore, a greater number of panicles/square m in wet sown rice could not compensate for number of spikelets/square m and number of grains/square m which was found in transplanted rice.