Drought Disaster Risk Threshold Value Determination of Maize Different Growth Period in Meitan

The evaluation model of agricultural drought disaster risk is built on the base of natural disaster risk theory selecting maize as research subject and Meitan as research area; it includes agricultural drought disaster hazard, exposure, vulnerability and drought resistant ability. Trend yield is simulated by three time’s polynomial simulation; relative meteorological yield can be calculated by excluding trend yield from real yield. The relation analysis is done between risk value and relative meteorological yield, the relative equation is established; the risk threshold and risk level of maize different growth stage are defined according to relative equation, crop disaster forming condition and drought level standard. The result show that critical risk value is minimal in seeding-emergence stage, reducing yield occurs easily due to drought when disaster forming condition is met, that is relative meteorological yield value is less than -5%; the possibility of reducing yield due to drought is more in earing -filling and jointing -earing period; drought influence is less in emergence -jointing and filling -mature period. It is coordinate with the fact that summer drought occurs frequently, spring drought occurs on occasion and maize grow characteristics.