Assessment of precipitation uncertainty on annual yield of dry farming Wheat

As the water resources are limited and about 40% of world’s farmlands use dry farming systems, improving the management of dry farming has great importance. The main purpose of this research is to investigate the impact of precipitation variability on annual yields of dry farming Wheat. The area under consideration is the province of Hamadan. All the probable time periods of precipitation have been considered and the impact of different periods of precipitation in 3 main cropping seasons (Autumn, Winter and Spring) was assessed on annual yields of dry farming wheat. Then the most effective period of precipitation on annual yields of dry farming wheat specified and the annual yield-effective precipitation regression relationship has been defined and calculated for this period. The values of annual yields of dry farming wheat were calculated based on a distribution function fitted to annual yield data and compared with values obtained from regression relationship. The results showed that the most effective period of precipitation on annual yield of dry farming wheat in all conditions, is March 30th to May 7th. Also, the results of annual yield-effective precipitation regression method in estimating of annual yields of dry farming wheat were similar to results of the distribution functions method with a correlation coefficient of 99%.