Deficit Irrigation of Cool and Warm Season Turfgrass Varieties under Sprinkler Irrigation Method

The aim of this study is to determine the effects of deficit irrigation applications at different levels on the cool-season and warm-season turfgrass species irrigated by sprinkler irrigation. Field experiments were conducted in the Agricultural Production and Research Center (TURAM) of Silivri Municipality in Gümüşyaka District located between the boundaries of Tekirdağ and Istanbul - TURKEY, at growing season 2019. In this research, two different turfgrass types (K: Cool season turfgrass and B: Warm season turfgrass), at three different irrigation threshold were examined in split-plots in randomized blocks design with three replications. Cool season turfgrass types lost its green colour completely after July due to the dry and hot summer season and the total amount of irrigation water applied in different irrigation strategies varied between 101.4 mm - 303.9 mm, seasonal evapotranspiration values varied between 217.7 mm - 391.5 mm, and daily evapotranspiration values varied between 2.4 mm/day - 4.3 mm/day. As for warm-season turfgrass types that managed to stay alive and kept its green colour throughout whole summer period; the same values varied between 203,6 mm - 591,6 mm; 328.4 mm - 593.9 mm; and 2,1 mm/day – 3,9 mm/day, respectively. In the 3-month period (May-June-July) in which both types of grass could survive, the seasonal evapotranspiration values were 11% more in the cool season turfgrass than that of warm season turfgrass. When daily evapotranspiration values were compared, it was observed that it was 10-14% more in cool-season turfgrass than in warm-season turfgrass. Average CWSI values calculated for different irrigation treatments were 0,57-0,66 for cool-season turf, 0,52-0,66 for warm-season turf besides, average CWSI values before irrigation application were 0,68-0,79 for cool-season turf, 0,69-0,79 for warm-season turf. Changes in the vegetation height, fresh yield, dry yield, plant density, color, and quality properties were monitored depending on the irrigation levels. When factors such as the amount of irrigation water applied, water-use and irrigation water-use efficiency, and quality parameters are evaluated together; none of treatments were adequate to keep cool-seasons varieties green after July. In the warm season turfgrass variety, although all irrigation levels provide the desired level for plant growth and quality, S2 treatment has been suggested when all parameters mentioned above are taken into consideration. Besides, Jensen Haise method (JH) was chosen as the best equation when reference evapotranspiration estimation methods were compared for both types of turf and crop coefficient (kc) curves have been prepared for both turfgrass species.