[Changes of rice yield and quality in different accumulated temperature zones in Heilongjiang Province of Northeast China].

Field experiments were installed in different accumulated temperature zones in Heilongjiang Province to study the changes of the grain yield and quality of five major rice varieties with accumulated temperature. The rice yield changed with accumulated temperature in quadratic curve, and the correlation degree differed with the varieties. The panicle number and the grain number per panicle changed significantly in quadratic curve with accumulated temperature, while the 1000-grain mass had less correlation with accumulated temperature. The sterile spikelet rate of grain increased obviously from suitable accumulated temperature zone to low accumulated temperature zone, but had no obvious change from suitable accumulated temperature zone to high accumulated temperature zone. The rates of chalky and head milled rice also changed with accumulated temperature in quadratic curve, i. e., there were both the lowest and the highest values in suitable accumulated temperature zone. The protein and amylose contents of the grain as well as the taste varied little with accumulated temperature. According to the sensitivity to temperature, the test rice varieties were divided into sensitive, medium, and blunt types, with the optimal and allowable cultivation accumulated temperature limits being 300 degrees C and 420 degrees C, 360 degrees C and 440 degrees C, and 380 degrees C and 520 degrees C, respectively. It would be very important to select the rice varieties with higher yield and better quality according to the local conditions, especially the accumulated temperature.