Relationship of Varietal Differences and Growing Conditions of Paddy Rice to the Occurrence of Unclosed Glume Grains

Abstract

The occurrence of unclosed glume grains and cracked grains in the paddy rice harvested with combine harvester was recognized by Dr. Suetsugu et al. in 1965. Such abnormal grains are regarded as a problem which should not be overlooked from the viewpoint of process of drying of high moisture-content paddy rice grains. However, such abnormal grains can also be found in the paddy rice before they have been harvested. In the present report, the authors deal with the differences in the occurrence of such abnormal drains according to rice varietal differences and according to rice growing conditions. The test results may be summarized as follows: 1) Unclosed glume grains occur frequently in the case of early-maturing varieties, while occur very seldom in the case of medium-or late-maturing varieties. However, even in the cases of varieties similar in early-maturing, it is clear that the occurrence of abnormal grains varies according to varietal differences. 2) Even in the case of early-maturing variety in which unclosed glume grains are liable to occur, if the heading date is adjusted so as to be delayed to the extent of heading date of medium-maturing variety, the occurrence of unclosed glume grains would be reduced to the extent similar to the case of medium-or late-maturing variety. 3) In the cases of direct-sowing rice plants and densely transplanted ones, there is an increasing trend in the occurrence of unclosed glume grains, as compared with ordinary transplanted ones. 4) Both in the cases of ordinary transplanting and direct-sowing, it shows increases in the occurrence of unclosed glume grains when rice seed is directly sown earlier on the paddy field or when rice seedlings are transplanted earlier. 5) In case where nitrogen is decreased in the amount of application, and phosphate is increased in the amount of application, comparing with the standard application amount, unclosed glume grains will occur more frequently. The same trend can be seen in case where potassium is decreased in the application amoun. Sincere acknowledgment is expressed to Dr. Suetsugu, Director of the Fukui Prefectural Agricultural Experiment Station, for the fact that the above tests have been achieved under his expert direction.