Study on cultivation techniques of good taste rice in cold region of Hokkaido in Japan

In the northernmost Japan, Hokkaido, where with cold climate and changeable environment, to product good taste rice, the cultivation techniques for reducing amylose content and protein content were developed.Although amylose content is affected by cultivated rice varieties largely, early planting and seedling with large leaf stage are used in order to increase temperature during grain filling period by hastening heading date, since during mature period, the amylose content decreases along with the increase of temperature.About protein content, referring to the standard rate of nitrogen fertilizer application, analyzing the climate in 20 cultivation areas and in each 5 soil types, the standard grain yield is figured out based on previous grain yield and the target value of protein content is decided as below 7.0%.Amount of available nitrogen in soil, magnitude of air drying effect on ammonification, amount and duration of organic matter application are used to adjust that application rate.No top dressing, application of soil dressing in peat land and application of silicate fertilizer are needed.In order to increase initial growth, transplant ahead of time,close planting, shallow seedling, side dressing, and irrigating in the night or early morning to keep lower water temperature, wind break net and so on are used.The depth of water in the field can be increased during irrigation from panicle forming stage to booting stage in order to prevent occurrence of male sterility by cool weather.During grain filling period draining residual water at the proper time and after that retaining proper soil water are needed.Using rice straw after harvesting, compost is the best for high grain yield and low protein content and plowing-in is better in autumn than that in spring.