Research on drought assessment index of summer maize base on precipitation anomaly

The drought assessment index of summer maize was determined based on the relationship between precipitation and yield.Firstly,the history data series of yield were processed,trend yield was fitted using cubic polynomial,and the relative meteorological yield was detached;and then the relationship between precipitation anomaly in different growing phase and relative meteorological yield was analyzed.The result showed that precipitation anomaly from emergence to teaseling stage had significant positive correlation with relative meteorological yield.The regression equation was established through statistic analysis.The drought assessment index of summer maize in different grade was determined combined with division standard of agricultural drought.The index was: when negative precipitation anomaly was 20%,20%～50%,50%～80%,or 80%,the drought grade was slight drought,middle drought,heavy drought and serious drought,and the yield reduction was 10%,10%～20%,20%～30%,or 30%.