Studies on the Short Period Cultivation of Direct Sown Rice Plant : 3. Effect of the early stage growth of the rice plant under upland condition on the growth and yield after the water-logged period.

Abstract

This experiment was conducted on the direct sown short-period rice plant cultivated under upland condition in different seasons (early, ordinary and late), to know from the viewpoint of dry-mater production the effect of the upland period growth on the growth and yield after the water-logged period. 1. The rate of dry-matter increase per field area in the water-logged period through the early ear-forming stage was almost completely determined by the leaf weight index, and the higher the leaf weight index in the water-logged period, the higher the leaf weight index and the dry-matter increase rate in the above mentioned period. 2. In the period from early ear-forming stage through heading stage, the effect of the leaf weight index on the dry-matter increase rate was smaller than in the previous period in the case of early season cultivation while completely lost in the cases of ordinary and late cultivation. The effect of the net assimilation rate on the dry matter increase rate was not found either. There was a high positive correlation recognized in the leaf weight index between the water-logged period and the above mentioned late growth period. 3. In both periods mentioned above, the increase of the leaf weight index led to a decrease in the net assimilation rate. Since the relative growth rate was almost entirely governed by the net assimilation rate, difference in the top dry weight in the water-logged period decreased along with the advance of growth but did not disappear totally. 4. In the ripening stage there was no correlation found between the leaf weight index and net assimilation rate while they each had a positive relation with the dry-matter increase rate. Also the higher the leaf weight index in the water-logged period, the higher the leaf weight index and the dry-matter increase rate in the ripening stage. 5. It has been recognized that the dry-matter increase rate of the panicle in the ripening stage is largely determined by that of the top part in the same stage and the increase of the leaf weight index in the early growth stage is closely related to the high yield.