Studies On Loss Assessment Of Drought Disaster And The Impairment Measures Of Summer Maize In Henan Province

In this paper, the meteorological data and actual yields data of summer maize of96counties in Henan province from1971to2010were used to analyze the major factors of meteorological yield and the risk of yield loss of summer maize. By the methods of correlation analysis and the integral regression, the quantitative influence of precipitation on maize yield in different development stages was calculated by ten-day time step. The risk assessment indexes included the averaged yield reduction rate, variance coefficient of yield reduction rate, risk probability and risk index of yield-reduction of summer maize, and a comprehensive risk assessment indicator was established also in this paper. The risk regionalization of yield loss of summer maize in Henan province was completed. On the base of the field observation data, the daily meteorological data and the soil parameters data, the DSSAT-CERES-Maize model parameters are localized modification and validation, and was used to carry out the drought simulation test and impairment measures simulation of summer maize at different stages, and to evaluate impairment benefit. The main conclusions are as follows.(1) Through correlation analysis of meteorological yield with meteorological factors, the results showed that the rainfall and the average temperature were key factors which influencing the production of maize in western Henan, emergence to jointing stage and jointing stage to tasseling stage were the crucial climate stages to influent the maize yield. Sunshine and average temperature could meet the requirement of the maize growth in southern Henan; there was no significant correlation for precipitation for the whole stages, but there were significant negative effects in mid-September. The sunshine, heat and water conditions are proper in irrigated areas and drought rarely occurred. At the stage of sowing to jointing, precipitation had obvious positive effects to maize yield in western Henan and at the stage of jointing stage to tasseling will appear drought. At the milking stage, precipitation had negative effects on yield in southern Henan, yield decreased with the increase of precipitation by the reduction rate of11kg·hm-2·mm-1. The "early summer drought" and "the card neck drought" could occur in northern and eastern Henan.(2) According to the comprehensive risk index, summer maize planting region in Henan province can be divided into three risk categories of high, medium and low. The low risk area included the plain areas of northern and eastern Henan, middle parts of Henan and Nanyang Basin; the medium risk area included western hilly area and southern rain-fed summer maize area, and the high risk area included Xincai, Shangcai, Pingyu, Shenqiu and Mianchi counties which had the highest yield-reduction risk and weaker anti-disaster ability.(3) According to the rainfall year type divided by the precipitation assurance rate, the drought years of1991,2002and2007were selected to carry out simulation test and the impairment simulation by the validated model of DSSAT-CERES-Maize. Impairment irrigation simulation results showed that, irrigation could greatly reduce the drought damage rate of summer maize, the averaged impairment rate was larger with twice irrigation than that with once irrigation, in the early days of filling stage is the key period for grain formation and is the best irrigation period. Water use efficiency in twice irrigation treatment was larger than that in once irrigation treatment, while the treatment including the irrigation in the early days of filling stage had the most obvious effect for water saving and loss reduction.In the actual agricultural production, irrigation is usually determined according to the period and degree of drought which could be forecasted by actual soil moisture and precipitation. If severe drought occurred during the whole stages on drought year, it is suggested that irrigation could be given by three times at jointing, flowering and milking stage, respectively in the areas with good irrigation condition. For periodic drought, irrigation could be given according to specific situation. While in the areas with poor irrigation condition and high cost of irrigation, it is suggested that the irrigation gives in once, at the early stage of filling.