Nitrogen and Light Affect Water Use and Water Use Efficiency of Zoysiagrass Genotypes Differing in Canopy Structure

Abstract

Irrigation of residential lawns represents one of the major uses of potable water in many regions. An increased understanding of physiological responses underlying effects of turfgrass genotypes and management practices on water use rates and water use efficiencies could contribute to water conservation. Thus, we evaluated the effects of nitrogen (N) fertilization (0.0 and 2.5 g·m−2) and light environment (full sun and 50% shade) on average daily evapotranspiration (ETAVE), daily ET per unit leaf area (ETLA), carbon exchange rate (CER), and water use efficiency (WUE) in upright (experimental TAES 5343-22) and prostrate (‘Empire’) zoysiagrasses (Zoysia japonica Steud.) during two repeated trials. Across all treatments, ETAVE was 4.0 and 5.4 mm·d−1 during Trials 1 and 2, respectively. In the upright-growing genotype, ETAVE was ≈10% greater than the prostrate genotype during Trial 1. Nitrogen fertilization increased water use by ≈20% compared with non-fertilized pots. However, N fertilization reduced ETLA and increased WUE. Thus, ETAVE was positively related with WUE. As a result, there was a tradeoff between ETAVE and WUE, indicating that efforts to achieve reductions in water use through low N fertilization or genotypes can be accomplished, but in some cases at the expense of using water less efficiently to assimilate carbon for plant growth processes. In turfgrass, reductions in growth and WUE might be acceptable to minimize water use, but vigor and quality need to be maintained.