Crop scientific studies on the yield-forecast of lowland rice. (Preliminary report) : VII. Forecasting number of ears per unit area in rice plant judging from the growth rate of its tillers

摘要

The studies reported in this paper were made as an effort to establish a method for forecasting ear numder of rice plant per unit area judging from its growing state. Experiments had been carried out in 1951∼52 to trace up the growing process of sterile tillers (which bear ears) and sterile tillers (which fail to head) with various rice-varieties under different culivating conditions, resulting in a fair success. The results obtained are summerized as follows : (1) Dates or the age of plant (as expressed by the number of leaves on the main stem) when tillers had emerged are not useful for distinguishing the fertile tillers. (2) The same is the case with the length or the number of leaves of individual tiller at the stage of floral initiation. (3) Tracing the growing process of fertile and sterile tillers, the authors found out the fact that after the maximum number of tillers had been attained, the velocity of increasing new leaves in an individual tiller is not equal with one another and tillers can be distinguished into two groups - one is normally fast and the other is slower in the velocity of appearance of new leaves and very few tillers took their place between two groups. Furthermore, they made it clear that tillers having the normal velocity of holding leaves became fertile in future and those with the slow velocity became sterile. This nature of tillers is thought to be most valuable in forecasting the future of tillers. (4) By applying this principle to nine varieties - early, medium and late - growing under six different conditions of cultivation, the authors ascertained that the number of ear could be predicted by this method at the time a week or, at the latest, two weeks after the stage of maximum number of tillers. (5) In general, in our investigations tillers having new growing leaf which is capable of elongating during a week over the length of about 60% of the finally attainable full length of the leaf blade of this leaf are promised as fertile tillers, those showing the elongation less than 30 percent became sterile, and those having leaf grown 40 ?? ?? 50 percent were very few and some of them became fertile and the others sterile. (6) In conclusion, this method of knowing the future of tillers, fertile or sterile, seems to be more reliable than any other method hitherto employed for predicting the number of fertile tillers ; because by this method only very few number of tillers are left to be unknown or misspredicted.