Abstract
Applying the method of deep-layer application of fertilizers in rice culture which has been populary practiced in Aomori Prefecture, the authors examined how yield and its components were affected by the planting density and the amount of fertilizers. The results of the experiment are summarized as follows: 1. As to the effect of the deep-layer application of fertilizers, the yield was increased by about 1-3 % on standard-planting plots, about 5-6 % on dense-planting plots, and about 10-11% on dense-planting and heavy-manuring plots, comparing with the control, respectively. Also the yield was higher by about 1-2 % on the plots in which seedlings from an upland nursery were used compared with those in which seedlings from a low-land nursery covered by vinyl film were used. 2. The number of panicles per square meter and the percentage of ripened grains decreased by the deep-layer application treatment, but increases in the number of spikelets per square meter and in the weight of 1000 kernels were observed. It was due to the increase in the number of spikelets per square meter that the percentage of ripened grains was decreased by the treatment, but aggravation in light-receiving habit also may have partly contributed to the decrease in the percentage of ripened grains. As light-receiving habit got better than in standardard planting plots, the percentage of ripened grains became higher in dense-planting plots and dense-planting and heavy-manuring plots. 3. The factor responsible for the increase in the number of spikelets per square meter by the treatment was considered to be caused by the increased rate of nitrogen content in leaf-blade and NAR at middle stage of growth. 4. At the same time, the husks were made bigger by this increase in the rate of nitrogen content in leaf-blade and NAR. High significant correlation was found between the size of husks and the weight of 1000 kernels. The former seemed to be one causes of increase in the weight of 1000 kernels by the treatment. 5. The size of husks might be correlated with the size of their pedicels and with that of conductive tissue existing in the pedicels. On the other hand, the effect of fertilizers might be maintained longer by the treatment. Therefore, it may be supposed that these effects by the treatment may have extended the activity of translocation.
