Index and Loss Estimation of Rain Washing Damage to Early Rice Pollen in Jiangxi Province

Rain washing damage to pollen is one of the main agrometeorological disasters of early rice in Jiangxi Province. However, there are few studies on the disaster index and loss estimation model of this disaster. And in routine agrometeorological service, there are no definite and targeted criterion and loss assessment basis of rain washing damage to pollen. Therefore, studies on disaster index and loss estimation mode of rain washing damage to pollen are of great importance to the disaster monitoring, loss assessment and agricultural disasters' insurance management of early rice. Taking the disaster of rain washing damage to pollen in Jiangxi Province as research object, 78 disaster samples of rain washing damage to pollen are picked out based on analysis of long-term (1981-2015) meteorological conditions during the whole growth period of early rice in 14 agrometeorological stations, and historical data about the observation of agrometeorological disasters, diseases and insect pests. Afterwards, index and loss estimation model of rain washing damage to early rice pollen are determined based on correlation analysis, normal distribution and principal component regression method, and verified by independent samples. Results show that the rainfall during heading-flowering stage of early rice has a significant effect on the formation of rain washing damage to early rice pollen. Main and key influence periods are 5 and 3 days before and after the heading-flowering stage, respectively. The daily precipitation 40 mm can be used as the threshold for rain washing damage to pollen in heading-flowering stage of early rice. Based on this index, the number of days with total precipitation exceeding 40 mm and their corresponding accumulative precipitation are counted. When the accumulative precipitation is between 40 mm and 170 mm (light disaster), the yield reduction rate of early rice is generally less than 15%, and the average reduction rate is 10%. When the accumulative precipitation exceeds 170 mm (severe disaster), the yield reduction rate is generally more than 15%, and the average reduction rate is 22%. The grading indexes are detected to be basically consistent with the historical occurrence levels of rain washing damage to early rice pollen. And simulation results of loss estimation model show that simulated early rice yields are highly accordant with the actual yields, the average relative error is 4.3%, and the relative error of 78% data is within 5%. It indicates that the model can be used to simulate and predict the yield reduction rate of early rice when rain washing damages rice pollen.