WATER USE EFFICIENCY, YIELD AND YIELD COMPONENTS OF SECOND CROP SUNFLOWER UNDER DEFICIT IRRIGATION

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This study was conducted to observe the effects of different irrigation treatments on yield and yieldcomponents of second crop sunflower (Helianthus annuus L.) grown in western Turkey in 2012 and 2013.Trials comprised of two irrigation intervals (4-day and 8-day) and six different water levels (125, 100, 75, 50,25 and 00% of cumulative Class-A pan evaporation on a 4-day and 8-day interval basis) were investigated.Seasonal water use values varied between 191.1-662.6 mm in 2012 and 194.0-675.8 mm in 2013. Interactionsbetween irrigation interval and irrigation levels were found to be significant for seed yield in both years.Maximum and minimum seed yield were obtained from the 8-day IL-100 and 8-day IL-00 treatments asaveraging 5072.6 kg ha-1 and 2327.9 kg ha-1, respectively. Significant curvilinear relationships between seedyield and crop water use were obtained for 2012 and 2013. Water use efficiency and irrigation water useefficiency values were influenced by the irrigation intervals and levels. Water use efficiency varied from 1.21kg m-3to 0.70 kg m-3 among treatments in both years. The yield response factor (ky) was determined to be 0.70for 4-day irrigation interval and 0.69 for 8-day irrigation interval. Deficit and frequent irrigation caused aremarkable decline in all yield components (head diameter, stem diameter, plant height, 1000 seed weight andoil yield) investigated in both experimental years. The yield components decreased as irrigation levelsdecreased for each irrigation interval. The IL-100 treatment in 8-day irrigation interval could be proper forsunflower irrigated in semi-arid regions under no water shortage and the 8-day IL-75 treatment could be usedas a good basis for reduced drip irrigation strategy development under water shortage.