Supplemental Irrigation Requirements of Zoysiagrass and Bermudagrass Cultivars

Abstract

ABSTRACTMunicipal water restrictions have become commonplace throughout much of the southern United States. The objectives of this 2‐yr study were to (i) determine supplemental irrigation requirements necessary for achieving acceptable quality in 15 zoysiagrass (Zoysia japonica and Zoysia matrella) and bermudagrass (Cynodon ssp.) cultivars when managed under a 2 d/wk irrigation frequency, (ii) determine the effects of mowing height on irrigation requirements, and (iii) evaluate root development differences between the species and cultivars at the completion of the study. A linear gradient irrigation system (LGIS) was used to provide an irrigation gradient across field plots. Plots were evaluated along the gradient six times over two summers to determine the level of supplemental irrigation, relative to reference evapotranspiration (ETo), necessary for maintaining acceptable visual quality. The fine‐textured, sports‐type bermudagrass cultivars required the least supplemental irrigation (∼10 to 15% × ETo) to maintain acceptable quality in the study. The medium‐textured amenity bermudagrasses and Japanese lawngrass (Zoysia japonica Steud.) cultivars required similar but somewhat greater irrigation requirements (∼15 to 20% × ETo) than the fine‐textured bermudagrasses. Manilagrass cultivars (Z. matrella) required the highest supplemental irrigation requirements (∼25 to 33% × ETo) for maintaining acceptable appearance within 2 d/wk irrigation regime. Mowing height did not consistently affect irrigation requirements for either group of bermudagrass but affected the Zoysia species differently. Tall mowing heights generally reduced irrigation requirements in Z. japonica but increased irrigation requirements for Z. matrella cultivars. While few intraspecific root development differences occurred within the 0 to 25 cm soil depth, Z. matrella root development was limited relative to bermudagrass and Z. japonica cultivars within deeper (25–50 cm) soil, which may have contributed to the higher irrigation requirements for the species. The results emphasize differences in supplemental irrigation levels needed for maintaining acceptable appearance among warm‐season turfgrass species and cultivars during 2 d/wk irrigation.