Effect of hydrothermal factors on sunflower yield in the Azov area of the Rostov region

From 2011 to 2024, a longterm multifactorial experiment was conducted on the slope of the Bolshoy Log ravine in the Aksai district of the Rostov region. Various crop rotations, fertilizer application levels, and methods of primary soil treatment were studied. The research aimed to determine the optimal combination of hydrothermal factors (average daily air temperature, total precipitation) for obtaining high and stable sunflower yields in the conditions of the Azov district of the Rostov region. The research revealed an increase in air temperature during the sunflower growing season with a simultaneous decrease in precipitation. Depending on the fertilizer application rate, sunflower yield ranged from 1.44 to 2.21 t/ha. A slight effect of precipitation on sunflower yield and a strong negative effect of average daily air temperature were identified. The optimal conditions for obtaining high sunflower yield in the Azov district were determined to be an average daily temperature of no more than 22.0 °C and more than 300 mm of precipitation during the growing season. Increasing the fertilizer application rate provides a cost recovery in the form of an increased yield of 4.5–6.0 kg of seeds/kg of active ingredient when the average daily air temperature increases to 23.5 °C and the amount of precipitation decreases to 160 mm during the growing season.