Turfgrass Evapotranspiration. I. Factors Influencing Rate in Urban Environments1

Abstract

Evapotranspiration (ET) by turfgrass in urban environments is site specific and can vary considerably from what would be predicted from regional climate. A large degree of heterogeniety exists in residential microclimate and lawn management practices. The relative importance of these factors needs evaluation to aid in planning for efficient use of municipal water, half of which is applied to lawns in some western areas. This study, using small lysimeters, evaluated the relative effects of mowing height, N fertility, shading, grass species, and soil composition on ET. Kentucky bluegrass (Poa pratensis L. var. ‘Merion’) mowed 5 cm used 15% more water than grass mowed at 2 cm. Thirteen percent more water was used when 4 kg/1000m² of N was applied each month during spring and summer compared to only one application for the season, applied in the spring. Evapotranspiration by grass in 1979 was essentially the same whether growing on a clay soil or on a sand‐peat mixture; however, a 6% decrease occurred for the soil system in 1980. Evapotranspiration increased linearly with solar radiation when an advective component of energy, accounting for 35% of ET, was subtracted from all solar treatments. Kentucky bluegrass and tall fescue (Festuca arundinacea Schreb. var. ‘Rebel’) which are cool‐season grasses, used over 20% more water than bermudagrass (Cynodon dactylon L. X Cynodon transvaalensis Davy var. ‘Tifway’) and buffalograss (Buchloe dactyloides Nutt) which are warm‐season grasses.