Effects of Water Supply During Stage of Before-heading on Filling Dynamics and Yield of Rice in Cold Regions

With Kenjian 5Rice as experimental materials,the effects of water supply during the stage of before-heading on filling dynamics and yield of rice in cold regions were studied with pots under rainproof shelter.Water dynamics in the pots were monitored by examining soil water potential(SWP)using negative pressure soil moisture tensiometers.The results indicate that intermittent irrigation at SWP between-8～-10kPa increased economic yield of Kenjian 5Rice significantly,along with increases of average growth rate(■)and maximum growth rate(Gmax)of the superior grains and inferior grains and decreases of ■ and Gmaxof the middle grains.The index I values of superior grains and middle grains were improved,despite those of the middle grains.The growing active days(D)were shortened for the superior grains,while elongated for the inferior grains and middle grains.The weight per 1 000grains(WmaxG)was increased for all the three grades of the rice grains.On the contrary,with unremitting irrigation at SWP between-18～-20kPa and-28～-30kPa during the stage of before-heading,economic yield of Kenjiandao 5were significantly reduced,indicating by increased ■ and Gmaxvalues for the superior grains and decreased ■ and Gmaxvalues for the middle grains and inferior grains,and raised I values,shortened Dand increased Wmax.Gfor the grains of all the three grades.