Grain filling properties and characteristics of yield and grain quality of direct-seeded rice (Oryza sativa L.) in Tohoku district [Japan]

The characteristics of yield and grain quality of direct-seeded rice in Tohoku region was investigated under 'a cooperative experiment for analysis of grain filling properties in direct-seeded rice'. The experiment was carried out at the prefectural agricultural experiment stations in the Tohoku district and at the National Agricultural Research Center for Tohoku region, in order to clarify the constraints for stabilization of yield and grain quality in the direct-seeding cultivation from 2004 to 2006. The yield of direct-seeded rice decreased about 10% due to decrease in the total number of spikelets, compared to that of transplanted rice, although grain filling rate did not decrease and weight of 1000 grains increased in direct-seeded rice. In case of the decrease in the total number of spikelets derived from lower number of spikelets per panicle in direct-seeded rice, the lower percentage of spikelets at 2nd rachis branch on the panicle, which is favorable for stabilization of the grain quality, was shown. And it is suggested that the direct-seeding cultivation is effective for the higher percentage of perfect grains because of the lower temperature at ripening period due to the delay of heading time. Furthermore, although the amylose content of grains in direct-seeded rice increased, the difference with that in transplanted rice was smaller than that affect on the taste quality. Hereafter, it is important to improve the cultivation method on the basis of knowledge in the experiment.