Abstract
This study was undertaken to estimate the optimum time to harvest the grains of winter wheat with high amylogram viscosity. In 1996 and 1997, three characteristics;kernel weight, grain moisture content and falling number of two cultivars, Chihoku-komugi and Hokushin, were determined during the ripening stage. The samples were taken from five different field locations in Hokkaido. In both years, the time of maximum grain weight (Tmax), which indicates physiological maturity, varied with the weather conditions during the ripening stage. Grain moisture content decreased gradually to 40% at a similar rate in all cases, but the rate of decrease below 40%, decrement in moisture content varied with the field location and year (weather conditions). In 1996, grain viscosity started to increase late and slowly, the maximum falling number being less than 300 sec in many locations. In 1997, the viscosity started to increase earlier 32 to 34 days after heading. Hokushin had a higher falling number and kept the viscosity value of over 300 sec for a longer period than Chihoku-komugi. It was concluded that in order to avoid low amylogram viscosity, we have to harvest the grains when the falling number is over 300 sec. This is because at this stage, Tmax had already been reached.
