The crop-water level response model of rice under alternate drought and waterlogging

In order to investigate the relationship between paddy rice subjected to alternate drought and waterlogging and water level, the water level was used as the index of field water status and the suitable water level for water-saving and high yield at each growth stage of rice was determined, which is expressed as [H-min,H-i, H-max,H-i]. The degree of waterlogging was measured by the index of SFWHmaxi,, which represents the accumulation of flooding depth that the water level of the i(th) growth stage is more than the upper limit of the suitable water level. The degree of drought was measured by the index of SEWHmin,i, which represents the accumulation of water depth that the water level of the i(th) growth stage is less than the lowest limit of the suitable water level. The crop-water level response model (MCRWL) of the relationship between crop relative yield (R-y) and two indexes was established. The drought and waterlogging sensitive indexes of paddy rice under alternate drought and flooding were calculated by the test data of 2007-2008 with regression analysis method. The results showed that the two indexes could preferably reflect the sensitivity of each growth stage of rice under alternate drought and flooding. The parameters had an important scientific value and practical significance in optimization of irrigation-drainage management policy in rice irrigation area. In addition, it was very useful to guide the practice of irrigation and drainage.