The Climatic Zoning of Spring Maize in Hunan Based on Meteorological Disaster Indexes

The maize is the biggest drought grain crop in Hunan, the single yield is lower than the average of the country about 450 kg/hm², moreover, the total yield is very difficult to reach the practical demand. So considering the reduction of the meteorological disaster's risk, and carrying out the maize plant zoning, it is expected to arrange well the distribution and provide scientific foundation to prevent and avoid disasters. The climate factor are defined in zoning index in crop climate zoning research in the past, the grade division is the main method. Plant zoning will be carried out according to the meteorological disaster index which will restrict the spring maize high and stable yield.Based on the historical meteorological data of 97 weather stations in Hunan from 1961 to 2004, combined with the ecological habit of maize and field experiment data results, the disaster index is calculated in maize growth. This index includes the drought from maize spin to maize autumn, high temperature damage and protracted rain spell at the stage of seeding, and it affects significantly in maize growth. At the same time, these indexes are used to maize plant zoning. The three disasters of the zoning distribution character are systematic analyzed in City-star software. The protracted rain spell annual probability is from 23.3% to 86.7% at the stage of seeding, the terrain distribution tendency is more in the south than north. The drought annual probability is from 4.6% to 45.5% at the procreate growth, the tendency is that the west of Hunan and the south of center Hunan has much high probability, there is small probability in the Zi River valley and the Dongting Lake region. The high temperature damage annual probability is from 0 to 81.8% from spin to autumn, there is high occurrence probability in Hengyang, the south of center Zhuzhou; but there is low occurrence probability in the Dongting Lake region, the west of Hunan and the hilly southwest Hunan, the mountainous southeast Hunan. The annual probability of disaster index is used. At the same time, the "variable speed" theory is introduced. The climate factor is not only the integral grade, but also fine variable. The zoning grade according to disaster factor for maize growth influence is used. The drought occurrence annual probability grade index is K_d=P_d/0.25. The high temperature damage occurrence annual probability grade index is K_h=P_h/0.30; protracted rain spell occurrence annual probability grade index is K_c=P_c/0.50. At last, the total grade index is reached, it is K=K_d+K_h+K_c. The spring plants are divided into four regions according to the synthesis grade index.The results show that most regions are adaptable to plant maize in Hunan, whereas the adaptability is different in different areas. The high yield region distributes in the optimum region and suitable region; the low yield region distributes in the relatively suitable region and sub-suitable region. But the low yield region in the southeast of Hunan is in the suitable region, the causes for that may be the lack of sunshine and temperature in the mountainous region and the soil fertility is bad.