The role of Climate Parameters on Wheat Yield at Rainfed Regions of Kohdasht and Poldokhtar of Lorestan Province

Crop growth and production at rainfed systems is related to climate parameters changes. Climate parameters changes influenced Crop growth and its production at rainfed systems. Assessing the effective parameters and planning for their managing and or arranging agronomic activity with those trend changes، which result to improving production baseline and prediction for future. Precipitation and temperature are more important climate factors، which influence crop growth and production. Assessment the components of these factors، lead to improving grain yield and rain water productivity. In order to estimation of climate-yield production functions، analyzed eight crop seasons data (1998-2006) of 25 climate parameters and rainfed wheat grain yields of two warm regions of Lorestan province including Kohdasht and Poldokhtar. By path analysis method separated correlation coefficient to direct and indirect effects. Statistical indicators such as mean absolute error، maximum absolute error، root mean square error، index of agreement and efficiency were used for evaluation climate models. Relationship between precipitation – yield and precipitation – water productivity، determined for this area. Results showed that in local and common models of production functions، the role of sunshine is very important. Sunshine influenced relative humidity and air temperature، and then affected on yield and rain water productivity. The local models necessary small input data but common model need more input data (Tmin، n، PWimter، PStart، PEnd، Tmin-abs، PAban، PAzar، PDay، PFar، POrd، Tmax-far.). Statistical indicators amounts، showed that، the climate models were suitable to yield predict at these regions. Rain water productivity of all regions determined for eight crop seasons، and amounts of maximum، minimum and average of rain water productivity were 0. 411، 0. 142 and 0. 269 kg per cubic precipitation، which its average was 8 percent lower than national average (0. 292 kg. m-3). We conducted the climate-yield models are useful tools to predict rainfed wheat yield and so to assist managers and farmers for making decisions in rainfed agronomic activity under climate parameters changes.