Abstract
This study is analogous to the studies which were previously reported by the authers.This time, the most adequate amount of potassium to be given to rice plants in a paddy field condition is determined by the same method that was applied in the case of nitrogen and phosphorus.And the following results are obtained. 1)If we make a graph (as shown in Fig.3) which shows the relation between the amount of the grain produced and the percentage content of potassium in the grain at a given amount of potassium application, two stages are recognized from it.That is, the first stage is the normal stage and the second the excess stage. 2)The point of inflexion from the first stage to the second, at which the highest yield, is in the case of 30 kg.K_2O per acre.At this point, the potassium (K_2O) content in the grain about 0.5%. 3)The degree of economic utilization of potassium is highest in the case of 7kg.K_2O per acre. 4)The starch content of rice increases and the crude protein content decresses according to the increment of potassium application.Higher content of crude protein in the case of lower potassium application is attributed to water and NaCl soluble protein.
