Evapotranspiration and irrigation scheduling of cool and warm season turfgrasses irrigated with sprinkler irragation method

The aim of this study is to determine the irrigation scheduling of cool-season and warmseason turfgrass species under sprinkler irrigation method. Field experiments were conducted in the experimental fields of Silivri municipality in Gümüsyaka village located between boundaries of Tekirdağ and Istanbul, during the summer of the 2018. In the study, three different irrigation strategies were applied on cool season and warm season turfgrass species. Experimental design was split-plots in randomized blocks design with three replications. In the experimental area, Bermudagrass (Cynodon spp.) was used as a warm season turf type and a four-part mixture (30% Lolium perenne, 25% Festuca rubra rubra, 35% Festuca arundinacea and 10% Poa pratensis) was used as cool season turf type. Irrigation scheduling was planned according to changes of available soil moisture level in root zone. Soil moisture values of 0-30 cm soil depth were used to determine the amount of irrigation water, and that of 0-60 cm soil depth were used for measuring of actual evapotranspiration. Irrigation water was applied when approximately 30%, 50% and 70% of readily available water at effective root zone of 30 cm was consumed and completed to the field capacity. For cool season turfgrass types; the total amount of irrigation water applied in different irrigation strategies varied between 523,5 mm – 275,3 mm, seasonal evapotranspiration values varied between 754,8 mm – 521,9 mm, and daily evapotranspiration values varied between 5,2 mm/day – 3,7 mm/day. As for warm season turfgrass types; same values varied between 423,8 mm – 186,2 mm; 590,1 mm – 521,5 mm; and 4,1 mm/day – 3,6 mm/day, respectively. Datas on, vegetation height, quality, surface coating, color, fresh yield and dry matter yield parameters were collected in the study. In conclusion, the effect of different irrigation levels on two different turfgrasses have been determined to be statistically significant. When factors such as amount of irrigation water applied, water-use, efficiency cutting frequency and quality parameters under the region's conditions are evaluated together; it is suggested to start irrigation when approximately 50% of the available water in effective root zone is consumed for cool season turfgrass and when approximately 70% is consumed for warm season turfgrass. Average CWSI values calculated for different irrigation treatments were 0,19-0,45 for cool season turf, 0,19-0,32 for warm season turf besides, average CWSI values before irrigation application, by other words irrigation threshold for suggested treatments, C1S50 and C2S70, were 0,52 and 0,65, respectirvely. When suggested applications are compared, it has been determined that warm season turfgrass demands 63% less irrigation water and consumes 28% less water than cool season turfgrass. Besides, the most suitable reference evapotranspiration estimation methods under the experimental condition are Penman-FAO modification (P-FAO) and Penman-Monteith (P-M) method for cool season and warm-season turfgrass species, respectively, and crop coefficient (kc) curves have been prepared for both turfgrass species.