Deficit irrigation effects on water use characteristics of bentgrass species

This study was designed to determine the effects of deficit irrigation on water use traits of colonial (Agrostis capillaris L.), creeping (A. stolonifera L.), and velvet (A. canina L.) bentgrasses and to compare their water use. Field experiments were conducted from July to November in 2002 and 2003. Plots were irrigated at four levels of irrigation based on the percentage of actual evapotranspiration (ET_a): 100, 80, 60, and 40% ET_a replacement. The influence of deficit irrigation on water use was evaluated by measuring soil water depletion (SWD) and water use efficiency (WUE). The WUE was quantified by the ratio of canopy net photosynthetic rate to transpiration rate and carbon isotope discrimination (CID). Evapotranspiration (ET) rates were compared among the three species under nonlimiting moisture conditions (100% ET_a). Our results demonstrated that water use characteristics varied with species, irrigation regime, and climatic conditions. Irrigating at either 60 or 80% ET_a had no significant effects on WUE compared with 100% ET_a irrigation; however, plots irrigated at 60% ET_a exhibited higher SWD compared with plots at 80 and 100% ET_a. Velvet bentgrass exhibited lower SWD, higher WUE, and lower CID compared with colonial bentgrass during the summer treatment period, and creeping bentgrass exhibited intermediate water use characteristics among the three species. These results suggest that irrigating bentgrass species at 60 to 80% ET_a could be practiced to increase WUE during summer and 40% ET_a during fall months under the conditions of this study.