Studies on Yield-Forecast in Main Crops : IX. Comparison of growth and process of grain production in the direct seeding culture of paddy rice with those in the transplanting culture.

Abstract

For purpose of finding the method of yield-forecast in paddy rice directly sown, growth and process of grain production in it were investigated under field conditions comparing with those in the transplanting culture, using variety "Mihonishiki" in 1962. The main differences between them were as follows: 1. In the direct seeding culture, the number of leaves on main stem was fewer and the number of tillers per unit area was numerous, but percentage of available tillers was lower than those in the transplanting culture. Secondary tillers in the direct seeding culture were all dead. 2. Rice plant in the direct seeding culture had more panicles but fewer spikelets per panicle than that in the transplanting culture. The ripening of rice grain (yield per 1, 000 spikelets) was about the same, but the weight of 1, 000 kernels in the direct seeding culture was a little lighter than that in the transplanting culture. The relation between the yield and the number of spikelets per unit area did not differ between both cultivation. 3. The area and the nitrogen content of leaf blade of rice plant in the direct seeding culture were both larger than those in the transplanting culture at early stage of growth, but such relation was gradually reversed later on. Light-receiving coefficient in the direct seeding culture was inferior to that in the transplanting culture, but mean photosynthetic ability on leaf weight basis showed no difference between both cultivation. Photosynthetic ability of the rice community under field condition in the direct seeding culture was inferior to that in the transplanting culture at almost every stages except the early stage of growth.