Studies on the Short Period Cultivation of Direct Sown Rice Plant : 1. Effect of nitrogen and seeding density upon the eraly growth of the rice plant.

[摘要] A series of experiments was conducted on the direct sown rice plant cultivated under upland condition in early, ordinary and late seasons, respectively, by varying the nitrogen application amount as basic manure as well as the seeding density. Amount of nitrogen applied in three plots was 0.3 kg/a, 0.6 kg/a and zero, respectively. Number of grains sown in each plot which was divided into four was 200, 400, 600 and 800 per m2 respectively. In the case of ordinary cultivation another pot was laid out in which dicyandiamide was added to nitrogen. Observations were continued up to the 4th leaf stage on the nitrogen content of soil and the growth of rice plant. Results obtained are as follows. 1. In any growing season, the nitrogen content of soil depended on the amount of nitrogen applied, but the loss of nitrogen applied as basic fertilizer was quite heavy due to nitrification. 2. Nearly total disappearance of the 0.3 kg/a basic nitrogen manure occurred in the 1st to 2nd leaf stage with the early season rice plant, in the 2nd to 3rd leaf stage with the ordinary season and in the 3rd leaf stage with the late season. 3. Nitrification was checked by addition of dicyandiamide to ammomium sufate, which re resulted in a remarkable effect on the growth of rice plant. 4. Growth of the rice plant improved in proportion to the amount of nitrogen applied in basic dressing but there is little difference in growth between the non-nitrogen and 0.3 kg/a plots, while a big difference between the 0.3 kg/a and 0.6 kg/a plots. Dry matter weight of individual plants decreased as the seeding density increased, and the same tendency was found with the nitrogen content of rice plant.

[学科分类] 农业科学（综合）