Effects of Turfgrass Species and Irrigation Practices on Carbon Fixation and Water Use Efficiency

Turf is an essential part of urban landscapes and an effective sink for soil organic carbon, yet little is known about the relative carbon fixation (CF) capabilities among various turfgrass species and cultivars and how CF is influenced by irrigation practices. Ten commonly used cool-season and warm-season turfgrasses were evaluated for CF and water use efficiency (WUE) rates under optimal and deficit irrigation practices. Cool- season species consisted of: Kentucky bluegrass and perennial ryegrass (KB/PR); fineleaf fescue (FF); tall fescue and Kentucky bluegrass (TF/KB); and tall fescue (TF). Warm- season species included: zoysiagrass (ZOY); st. Augustinegrass (SA); seashore paspalum (SP); bermudagrass (328B and 419B); and buffalograss (BUF). CF was measured and calculated as gross ecosystem productivity (GEP) along with WUE using an open-path infrared gas analyzer. KB/PR, FF, TF/KB, TF, and SP had the highest GEP under deficit irrigation. When grouped, GEP was significantly higher during recovery under deficit irrigation (p<0.0001) for cool-season compared to warm-season turfgrasses, indicating that C3 photosynthesis is labile and C4 photosynthesis is stabile during recovery. Overall, WUE for warm-season grasses was higher than cool-season grasses (p<0.0001). However, species did not differ in WUE between optimal and deficit irrigation, suggesting that WUE is conserved when water is limited. Our results confirmed that warm-season turfgrasses are the most appropriate species for water conservation in regions where they are adapted.