Knowledge of relative drought resistance is important for selecting turfgrasses that persist during drought stress. Seven of the most commonly used turfgrasses in the Piedmont region of the humid Southeastern USA were evaluated in a field study under edaphic stresses common to the region for drought resistance and spatial rooting responses as a component of drought avoidance. Grasses were ‘Tifway’ bermudagrass (Cynodon dactylon × C. transvaalensis); common bermudagrass [C. dactylon (L.) Pers.]; ‘Meyer’ zoysiagrass (Zoysia japonica Steud.); common centipedegrass [Eremochloa ophiuroides (Munro.) Hack.]; ‘Raleigh’ St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze]; and ‘Rebel II’ and ‘Kentucky‐31’ tall fescue (Festuca arundinacea Schreb.). Grasses varied in drought resistance, as determined by wilt and leaf firing during dry‐down periods, from very high (Tifway and common bermuda), high (Raleigh St. Augustine, common centipede), medium‐high (Rebel II tall fescue), medium (K‐31 tall fescue), and medium‐low (Meyer zoysiagrass). High soil strength and acid soil complex stresses were present on the site. Under these stresses, deep rooting (20‐ to 60‐cm zone) in late summer ranged from Tifway bermuda (best) > Rebel II tall fescue = common bermuda > K‐31 tall rescue > Raleigh St. Augustine > common centipedegrass > Meyer zoysiagrass. Meyer produced only 4% of the root length density that Tifway did within this zone due to low genetic tolerance to the edaphic stresses. These results illustrate that genetic tolerance to edaphic stresses can markedly affect turfgrass rooting and drought resistance rankings. Plant breeders must give attention to edaphic stress tolerances if drought avoidance via roots is to be improved.

Multispectral radiometry provides a method for assessing plant light reflectance in the visible and near‐infrared ranges. Reflectance of narrow wavelength ranges as well as ratios of different ranges have been highly correlated with absorbency of photosynthetically active radiation, leaf area index (LAI), and plant response to stresses. The objectives of this research were to determine if data obtained by multispectral radiometry might accurately correlate with qualitative data (used as rapid estimates of color, density, and uniformity) typically used in turfgrass research. Furthermore, it was our objective to determine whether multispectral radiometry could discriminate between stressed and nonstressed turfgrass plots. This research was conducted in two consecutive trials during 1997 on seven seashore paspalum (Paspalum vaginatum Swartz) ecotypes and three hybrid bermudagrass (Cynodon dactylon L. × C. trunsvaalensis Burtt‐Davy) cultivars established on a native Appling (clayey, kaolinitic, thermic Typic Kanhapludult) soil at the University of Georgia Experiment Station in Griffin, GA. Reflectance at 661 and 813 nm, as well as the ratios normalized difference vegetation index (NDVI, computed as R935‐ R661/R935 + R661), infrared/red (IRIR) (LAI, computed as R935/R661), Stress1 (R706/R760 nd Stress2 (R706/R813) were highly correlated with visual turf quality, shoot density, and shoot tissue injury (STI) ratings, but not with shoot clipping growth. Regression analysis also indicated very strong associations with each of these qualitative variables, but not with shoot growth data. Additionally, spectral measurements at all wavelengths except 559 and 706 nm were able to consistently distinguish between wear‐treated and untreated plots. This methodology may have applications in both turfgrass research and management to provide quantitative measures with physiological significance to traditional visual qualitative estimates of shoot aspects.

Knowledge of drought‐resistance mechanisms in turfgrasses would improve management strategies and facilitate turfgrass breeding for drought resistance. The experiment investigated root morphological and physiological characteristics in response to surface soil drying and rewatering for bermudagrass [Cynodon dactylon (L.) Pers. ‘Common’], centipedegrass [Eremochloa ophiuroides (Munro) Hack ‘Tif‐Blair’], seashore paspalum (Paspalum vaginatum Swartz, four ecotypes), and zoysiagrass (Zoysia japonica Steudel × Z. tenuifolia Steudel ‘Emerald’). Plants were grown in sectioned PVC tubes with four soil moisture regimes in a greenhouse during 1995 and 1996. Root growth was reduced when the upper 20‐ and 40‐cm soil layers dried for Emerald zoysiagrass, Common bermudagrass, and Adalayd paspalum, but only with upper 40‐cm soil drying for PI 299042, AP14, and PI 509018 paspalums, and TifBlair centipedegrass. Root dry weight recovered fully to control levels after rewatering for TifBlair centipedegrass and the three paspalum accession, but only partially for Adalayd paspalum, Common bermudagrass, and Emerald zoysiagrass. Superior drought resistance to surface soil drying for PI 509018 paspalum and TifBlair centipedegrass was associated with enhanced root growth and rapid root water uptake at deeper soil layers, maintenance of root viability at the surface drying soil, and rapid root regeneration after rewatering. Differences in these drought avoidance characteristics among turfgrasses could serve as selection criteria for improving turf drought resistance.

In recent years, turf type tall fescues (Festuca arundinacea Schreb.) are being used for northern to mid‐South climates in the USA. Limited information is available on the diversity among cultivars of drought resistance and avoidance characteristics, which are important for persistence under drought and high‐temperature stresses. Four cultivars (‘Rebel H’, ‘Rebel Jr.’, ‘Kentucky 31’, ‘Bonsai’) and ‘GA‐5’ endophyte‐free (EF) and endophyte‐infected (El) with Acretnonium coenophialura Morgan‐Jones and Gams were evaluated in a field study at Griffin, GA, (using a clayey, kaolinitic, thermic Typic Haphidult soil) for intraspecific differences in overall drought resistance and for drought avoidance characteristics. These grasses provided a range in morphological traits. Overall drought resistance ranking based on decline in turf quality, leaf firing (LF), and/or wilt expression during dry‐down was Rebel II (best) > Rebel Jr., Kentucky 31, GA‐5‐EF, GA‐5‐EI > Bonsai. The magnitude of differences in drought avoidance characteristics among cultivars (least cuitivar = 100% base) for each year, respectively, were 213 (1991) to 200% (1992) for late summer root length density (RLD) at 20‐ to 60‐cm depth; 182 (1991) to 173% (1992) for total root length (TRL) lat e summer; and127%for evapotranspiration (ET) averaged over all water use periods (i.e., 1991 and 1992). Field measured ET rates revealed much lower ET rates (33–73% less) for the combination of humid climate and mild drought stress than reported in the literature for semi‐arid/arid and well‐irrigated tall fescue. Additionally, multiple regression analysis demonstrated that high RLD (20‐ to 60‐cm depth) was associated with less LF and wilt; maintenance of ET at 4 to 8 d after irrigation was related to less LF; and high RLD (3‐ to 10‐cm depth) related to greater LF and wilt. This suggests that high RLD in the deeper root zone and the ability to maintain ET as the soil dries are important for drought resistance of tall fescues.

Water‐use data obtained under the climatic and soil conditions typical of the southeastern USA are very limited. Seven of the most commonly used turfgrasses in the Piedmont region of the humid Southeast were evaluated in a field study under edaphic stresses common to the region for seasonal evapotranspiration (ET) and development of Class A weather pan coefficients (kp) and FAO Penman crop coefficients (k) for irrigation scheduling. Time‐domain reflectrometry (TDR) was used to determine ET for each turfgrass (i.e., ETc) during soil dry‐down periods in 1989 and 1990. Estimated ET by the weather pan and Penman methods was used with ETc to develop crop coefficients. Grasses were Tifway bermudagrass (Cynodon dactylon ✕ C. transvaalensis), common bermudagrass [C. dactylon (L.) Pers.] Meyer zoysiagrass (Zoysia japonica Steud.), common centipedegrass [Eremochloa ophiuroides (Munro.) Hack.], Raleigh St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and Rebel II and Kentucky‐31 tall fescue (Festuca arundinacea Schreb.). Average summer ET rates were common bermudagrass (3.03 mm d−1), Tifway bermudagrass (3.11 mm d−1), Raleigh St. Augustine (3.28 mm d−1), Meyer zoysiagrass (3.54 mm d−1), Rebel II tall fescue (3.57 mm d−1), Kentucky‐31 tall fescue (3.69 mm d−1), and common centipedegrass (3.80 mm d−1) with the latter two being significantly higher than the bermudagrasses ET rate. Observed ET values were 40 to 60% lower than reported for the same genotype from arid and semi‐arid regions under nonlimited soil moisture. Under humid environments, ranking grasses for drought resistance based on relative ET does not correlate well with field observations of drought resistance based on wilt and leaf firing. Crop coefficients for the same species were generally higher than those reported under less humid conditions. Warm‐season species exhibited different coefficients and could not be grouped together for a common coefficient. All grasses had substantial changes in coefficients over the growing season; thereby indicating the need for seasonal adjustments when using these for irrigation scheduling.