Grain Yield and Palatability of Rice Direct-seeded under Submerged Soil Condition in Hokkaido, in Northern Japan

Abstract

Grain Yield (GY), its components and palatability of rice direct-seeded under a submerged soil condition (direct-seeded rice, DSR) were compared with those of transplanted rice (TR) applying a similar amount of nitrogen fertilizer during 1997—2002 and 2004—2006 in Hokkaido. In central Hokkaido, three early maturity varieties (early MVs) were cultivated as DSR, and the early and three medium MVs as TR. In southern Hokkaido, the medium MVs were cultivated as DSR, and the medium and a late MV as TR. The heading date of DSR was 8.1—10.7, and 4.0—7.9 days later than that of TR with the same and one-rank later MV, respectively. The ratio of kernel number of GY to total ripened glumes and harvest index were lower in DSR than in TR. Thus, GY in DSR was only 76.9—99.7%, 86.9% on the average, of that in TR with a later MV, and promotion of growth after heading is needed for improving GY of DSR. In DSR amylose content was higher and the max value of gelatinization property was lower due to the lower temperature during ripening. The protein content in DSR was lower than that of TR in the same MV, but similar to that in TR with a later MV. Farmers cultivate earlier MV by direct seeding and DSR is disadvantageous for producing palatable rice.