Evapotranspiration and the response of cool-season and warm-season turfgrass species to deficit irrigation under a sprinkler irrigation method

Abstract

The aim of this study was to determine the effect of deficit irrigation applications at different levels on cool-season and warm-season turf irrigated by a sprinkler irrigation method. Field experiments were conducted in Istanbul, Turkey (41 & DEG;03MODIFIER LETTER PRIMEN; 28 & DEG;00MODIFIER LETTER PRIMEE; 46 m above sea level) during the growing season of 2019. In the study, two different turf types: a cool-season turfgrass mixture (C) and a warm-season turfgrass or Bermudagrass (W) were subjected to three different irrigation levels (I-1: Full irrigation, I-2: 1/3 deficiency, I-3: 2/3 deficiency) and examined in split-plots via a randomized complete block design conducted in triplicate. The soil moisture level was monitored via time-domain reflectometry (TDR) each day to provide irrigation timing. Unfortunately, none of the treatments were adequate to keep cool-season turf green after July because of a high MAD (Management Allowable Deficit) value. In the first 3-month period (May to July) of the experiment, during which both types of turf could survive, the seasonal evapotranspiration and the total amount of irrigation water applied were 11% more for the cool-season turf than for the warm-season turf. In the warm-season turf, although all irrigation levels provided for plant survival, the I-2 treatment is suggested when all quality parameters, such as the amount of irrigation water applied, the water used, the irrigation water-use efficiency and the quality parameters are evaluated together. Seasonal average values for Crop Water Stress Index (CWSI) were calculated for the different irrigation treatments ranging from 0.57 to 0.66 for cool-season turf and from 0.52 to 0.66 for warm-season turf. The average CWSI values before irrigation was applied were from 0.68 to 0.79 for cool-season turf and from 0.69 to 0.79 for warm-season turf. The Jensen-Haise method (JH) was chosen as the best equation when reference evapotranspiration estimation methods were compared for both types of turf.