Analysis of Yield-Determining Process and Its Application to Yield Prediction and Culture Improvement of Lowland Rice : LXVII. Studies on the principles for maximizing yield and their demonstration (1).

[摘要] With the view of (1) clarifying the principles for maximizing yield which can be applied in any sterile field and (2) demonstrating the principles, the authors tried to trace up, on the one hand, the processes determining high yields and, on the other hand, to demonstrate the possibility for obtaining high yields by controlling the growth of plants aiming at an "ideal plant". The characteristics of an "ideal plant" were proposed to be as follows: 1. The plant should have the necessary and sufficient number of spikelets per plant (per unit area) for obtaining a target yield. 2. The plant should be short in culm height as well as in panicle length and many in the number of culms for protecting lodging and increasing the percentage of ripened grains. 3. The upper 3 or 4 leaf-blades of the plant should be short, thick and errect for increasing the percentage of ripened grains (The "leaf-area index" should be nearly 5.). 4. The plant should keep absorbing nitrogen even in the period after heading for increasing the percentage of ripened grains. 5. The plant should have as many green leaves per culm as possible. (The number of green leaves per culm can be considered as an index of healthiness of the plant.) 6. The plant should emerge its heads in early August so that it may possess at least 20 fine days continuously after heading for increasing the amount of photosynthetic products at the ripening stage. On refering to these characteristics, the authors grew rice plants by water-culture and succeeded in obtaining 102 kg per are of brown rice which is much higher than the yield of the first prize in the competition of maximizing yield in 1962 in Japan. As a result of it, the authors proposed to practise the following items for raising the "ideal plant". (1) Use of healthy seedlings for making the plant absorb much nitrogen from the early tillering stage and ensure the necessary number of tillers as early as possible so as to obtain a target yield. (2) Decrease in supplying nitrogen or no supply of nitrogen during the growth stage from 70 to 90 in "leaf-number index" (which is corresponding to nearly 42-18 days before heading) for protecting lodging of the plant and for making the plant short in culm height, panicle length and also leaf length of 3 or 4 upper leaves and for making leaf-blades errect and thick. (3) Making the plant keep absorbing nitrogen even in the period after heading by top-dressing nitrogen just after the stage of reduction division of PMC (meiosis) or at the full heading stage for increasing the percentage of ripened grains. (4) Exclusion of toxic substances in soil by draining for increasing the healthiness of the plant.

[学科分类] 农业科学（综合）