Effects of different irrigation interval and plant-pan coefficient applications on yield and quality parameters of oil sunflower grown in semi-arid climatic conditions

Sustainability of plant production activities and improvement of irrigated lands in arid and semi-arid regions totally depend on efficient use of available water resources. Such an efficient use of water resources can be provided through assessment of water–yield relationships and identification of proper irrigation programs, schedules, and operational principles. There are no studies carried out to determine water–yield relations of oleic-type sunflower plants grown over large areas in Konya plain. In this study, different irrigation intervals (S) and crop-pan coefficients (Kcp) were used in drip irrigation of sunflower plants in Konya which is located at the Middle Anatolia in Turkey. The primary objective was to determine the effects of irrigation levels and intervals on yield and quality parameters of sunflower plants. Experiments were conducted in 2013–2014 growing seasons in 3 × 5 factorial design with 4 replications. Three different irrigation intervals (S<inf>5</inf>:5, S<inf>10</inf>:10, and S<inf>15</inf>:15-day) and five different crop-pan coefficients (Kcp<inf>1.25</inf>:125% of pan evaporation, Kcp<inf>1.00</inf>:100% of pan evaporation, Kcp<inf>0.75</inf>:75% of pan evaporation, Kcp<inf>0.50</inf>:50% of pan evaporation, and Kcp<inf>0.00</inf>:rain-fed without irrigation) were used in this study. In an average of 2 years, the greatest seed yield (5481 kg/ha) was obtained from S<inf>10</inf>Kcp<inf>1.25</inf> with the greatest water consumption (748.7 mm). As compared with S<inf>10</inf>Kcp<inf>1.25</inf> treatment, about 25% decrease was observed in yield of Kcp<inf>0.75</inf> treatments irrigated at 5- and 10-day intervals. Such a decrease was identified as 15% in Kcp<inf>1.00</inf> treatments irrigated at 15-day intervals. Therefore, for optimum seed yields from sunflower plants grown in Konya plain, irrigation intervals should not exceed 10 days. Also, crop-pan coefficient should be taken as 1.00 for high seed yields. Again, in an average of 2 years, irrigation water use efficiency (IWUE) of the treatments varied between 0.70 and 3.70 kg/m³ and water use efficiency (WUE) values varied between 0.53 and 0.75 kg/m³. The average yield response factor (k<inf>y</inf>) was identified as 1.14. Since the value is greater than 1, it was concluded that sunflower plants were sensitive to water deficits under Konya conditions.