thermal zoning of sunflower planting dates in the province of isfahan

abstract sunflower is one of the most important oilseeds in the world which has adaptation to high temperature. however, its cultivation in many different areas is neither desirable nor economical. considering that sunflower is a crop that is irrigated by adequate river water in the province of isfahan, temperature is a determining role in the final revenue. appropriate temperatures are shown at different stages of the plant growth and its development in suitable planting dates. in order for the thermal zoning of sunflowers’ cultivation in the province of isfahan, temperature data from 41 synoptic and the climatology stations in the province of isfahan and its neighboring provinces from their establishment to the year 2010 were utilized. the province zone was divided into three temperature zones (1, 2 and 3) using the day and night temperatures average by kriging method. to determine suitable planting date for sunflowers in spring and summer in isfahan, the average means of 15 days temperature from february 4 to november 21 were calculated and the regression equation between height and temperature was obtained. then, suitable planting dates, determined in each temperature zone due to the thermal needs of the crop and the maps, were drawn using dem in gis environment. based on the results, sunflower cultivation begins on february 20 from the east of the province and then all the other parts gain the temperature needed to grow until the second half of may. according to the sunflower thermal needs, if this plant is planted in different regions on suitable planting dates, it will not face inhibitor temperatures and suitable efficiency is achieved in terms of the climate. also, second cultivated sunflower is done in the central and surrounding areas of isfahan and cultivated sunflower is possible in the central areas of the province in july and august.