Thermal Zoning of Spring Safflower in Isfahan Province, Central Iran

Many crops are grown in regions and sowing dates which the climate is not in the desirable condition, bringing about decreases in efficiency of agricultural inputs and crop yield.  The spring safflower is planted under irrigation condition in Isfahan province and the temperature during growing season plays a major role in its seed yield.  For thermal zoning of spring safflower planting in Isfahan province, the temperature data from 51 synoptic and climatologic stations of Isfahan and neighboring provinces from 1961 to 2009 were used. Thermal zoning was determined based on mean day-night temperatures and the province was divided into three thermal zones by Kriging method. In each region considering thermal requirement for the plant establishment the thermal zoning in GIS was delineated, using radial basis function. According to the results in the first thermal region (which mainly covers the warm section of Isfahan province) the best planting date is from late January to late February. In the second zone (which mainly covers the temperate region of Isfahan province) the best sowing date is from early-March to early-April. The third zone (which is consisted of cold region) the suitable planting date is from early-April to early-May. Considering the thermal requirement of safflower, if it is planted in different parts of Isfahan according to the above planting windows in each region it will not face with adverse temperature conditions, and will take full advantage of growing season and may lead to increase in seed yield.