Penman Monteith Crop Coefficients for Use with Desert Turf Systems

Abstract

Irrigation scheduling systems which estimate actual evapotranspiration (ETa) by adjusting reference evapotranspiration (ETo) with crop coefficients (Kcs) have been suggested as a means of improving irrigation management of turfgrass in the desert southwest. The objective of this study was to develop turfgrass Kcs for use with ETo computed by the Penman Monteith Equation recommended by the United Nations Food and Agricultural Organization (FAO). Crop coefficients were developed for fairway quality ‘Tifway’ bermudagrass (Cynodon dactylon L. × C. transvaalinsis Davy) in summer and overseeded ‘Froghair’ intermediate ryegrass (Lolium perenne × L. multiflorum) in winter by relating daily measurements of ETa obtained from weighing lysimeters to ETo computed with meteorological data. Monthly and seasonal Kcs were developed by (i) computing the mean of individual daily Kcs, (ii) dividing cumulative ETa by cumulative ETo for the period, and (iii) computing the slope of least squares regression lines relating ETa to ETo. The three computation procedures did not greatly affect the resulting Kc value. Bermudagrass Kcs ranged from 0.78 in June to 0.83 in September, with monthly variation related to turf growth rate. Use of a constant Kc of 0.80 would suffice for estimating ETa in summer. Monthly Kcs for intermediate ryegrass ranged from 0.78 in January to 0.90 in April and varied in relation to mean air temperature. Increased bulk surface resistance resulting from chill‐induced reductions in stomatal conductance and/or a reduction in turf growth rate and leaf area index may lower ETa and Kcs during the colder winter months, making use of a constant seasonal Kc less suitable in winter. An inverse linear relationship was obtained between the coefficient of variation of mean monthly Kc and the ratio of measured to theoretical clear sky solar radiation, indicating Kcs are less reliable during periods of cloudy weather.

Irrigation performance in private urban landscapes: A study case in Zaragoza (Spain)

“…In this work, a k s value of 0.82 was assigned to turf. This value is consistent with the high requirements of these species and was obtained as a weighted average of the values reported by Brown et al (2001). The k s value assigned to trees and shrubs was 0.55, corresponding to species presenting moderate water requirements.…”

“…This comparison is logical if most of the landscape area is turf. The second option is based on direct estimation of landscape water requirements through the use of instruments such as volumetric soil water sensors (Morari and Giardini, 2001;White et al, 2004) or weighing lysimeters (Brown et al, 2001). The last group of authors (Domene and Saurí, 2003;Contreras et al, 2006) follows the methodology proposed by Costello et al (2000), developers of the WUCOLS method for determining landscape water requirements.…”

Recycling industrial saline wastewater for landscape irrigation in a desert urban area

“…This is a modest amount of water use for irrigated landscape plantings in a desert environment. For example, Bermuda turfgrass can use in excess of 1 m yr À1 of water in Tucson, Arizona (Brown et al, 2001). Hence, saline water irrigation did not require unusually large applications of water to control salinity.…”

Integrating machine learning techniques and high-resolution imagery to generate GIS-ready information for urban water consumption studies

“…Costello et al 44 tabulated species factors for more than 2000 species in California, grouped into species with low, moderate and high water requirements. In this paper, a species factor ks of 0.82 is assigned to turf grass (compare the values reported by Brown et al 45 . Trees and shrubs were considered as species with moderate water requirements and a ks value of 0.55.…”