Study on Intermittent Irrigation for Paddy Rice：II.Crop Responses

Effect of intermittent irrigation on the production of paddy rice was studied in a well-puddled paddy field with four treatments and 2 replicates:continuou flooding irrigation(CFI),and intermittent irrigation Ⅱ-0，Ⅱ-1 and Ⅱ-2,in which plants were re-irrigated when the soil water potential fell below 0,-10,and -20 to about -10 or -20 kPa did not significantly affect the number of grains and the percentage of ripened grains .While,a lower crop growth rate(CGR) resulted from a decrease in the net assimilation rate (NAR) during intermittent irrigation Ⅱ-1 and Ⅱ-2,and there was also a reduction in the leaf area index (LAI) durin indtermittent irrigation Ⅱ-2.Senescence of lower leaves on stems was promoted in treatments Ⅱ-1 and Ⅱ-2 at the ripening stage .Early senescence at ripening stage and water stress around midday decreased the rate of photosynthesis in leaves,causing the lower NAR,These physiological responses of the plants were responsible for the reduction in the dry matter production and grain yield in the intermmittent irrigation treatments.