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.

tween species. Warm-season turfgrass is typically more wear tolerant than cool-season turf (Youngner, 1961; Traffic causes shoot injury to turfgrass, with resulting inhibition Beard, 1973). Cultural practices, such as increased mowof growth and reduction of quality. Turfgrasses in high traffic venues are generally selected for tolerance to traffic or for an ability to ing height (Beard, 1973; Youngner, 1961), moderate N quickly outgrow the injury. However, limited knowledge exists on fertilization levels (Kohlmeier and Eggens, 1983), and the mechanisms that impart wear tolerance to turfgrass, particularly a thatch layer (Beard, 1973) can also influence wear tolfor warm-season grasses. This field research was undertaken to assess erance. overall wear tolerance within and between seashore paspalum (Pas-While some research has looked at wear tolerance at palum vaginatum Swartz.) ecotypes and bermudagrass hybrids (Cynothe intra-specific level (Beard, 1973), the data are very don dactylon L. ϫ C. transvaalensis Burtt-Davy) and to determine limited as to the degree of severity in wear tolerance the mechanisms that contribute to wear tolerance for both species.within a species, and the specific mechanisms responsi-The research was conducted in two consecutive field trials during 1997 ble for enhanced wear tolerance. Anatomical, morphoon seven seashore paspalum ecotypes and three hybrid bermudagrass logical, or physiological plant characteristics correlating cultivars established on a native Appling (fine, kaolinitic, thermic Typic Kanhapludult) soil at the University of Georgia Experiment with wear tolerance across species may not be the same Station in Griffin, GA. Regression analysis determined that the most within a particular species. important potential mechanism related to enhanced wear tolerance Shearman and Beard (1975a) evaluated interspecies of seashore paspalum was reduced leaf total cell wall (TCW) content, wear tolerance with four measurements: visual ratings, which accounted for 51% of the variation. Other factors that enhanced percentage TCW content, percentage verdure, and perwear tolerance in this species were low leaf strength, low stem TCW, centage chlorophyll per unit area. They found that visual greater leaf moisture, greater shoot density, and higher K shoot tissue wear estimates were well correlated (r ϭ Ϫ0.98) with concentration. In bermudagrass, high stem moisture (40.9% of variaquantitative evaluations when evaluating wear tolertion) and reduced stem cellulose content (31.5% of variation) were ance between species. Canaway (1981) determined that associated with better wear tolerance. Other factors that enhanced percentage of ground cover remaining after wear was wear tolerance were greater stem and leaf moisture, shoot density, leaf lignin, stem and leaf lignocellulose, and concentration of K, Mn, negatively correlated with modified acid detergent fiber and Mg. Knowledge of these characteristics will assist in developing per unit area. screening protocols for selection of future wear toleran...

ential responses to N and K fertilization rates. Liberal N fertilization has increased shoot growth in numerous Hybrid bermudagrass cultivars (Cynodon dactylon L. ؋ C. transbermudagrass cultivars (Burton and Jackson, 1962; Wilvaalensis Burtt-Davy) differ in their responses to N and K for growth, total nonstructural carbohydrate (TNC) concentration, and turf qual-kinson and Langdale, 1974). Enhanced shoot growth ity scores. This 1995 research was conducted in Florida to compare has been at the expense of root growth in various turf responses of two bermudagrass cultivars to N and K under long-day species (Adams et al., 1974; Goss and Law, 1967; Madi-(Ͼ13 h) and short-day (Ͻ13 h) conditions in a glasshouse. Evaluations son, 1962), although Horst et al. (1985) reported inwere made concerning shoot and root growth, TNC concentration, and creased root growth in response to N at rates up to 4.9 quality scores of 'FloraDwarf ' and 'Tifdwarf ' bermudagrass during g m Ϫ2 per growing month on 'Santa Ana' bermudagrass. establishment in a coarse sand medium. Experimental design under Potassium at rates up to 22.4 g K m Ϫ2 yr Ϫ1 increased each photoperiod was a randomized complete block with factorial root or rhizome weights in 'Coastal' bermudagrass (Keitreatments consisting of two cultivars, four rates of N, four rates sling et al., 1979). Shoot growth in Coastal increased of K, and four replications. Data were analyzed by fitting multiple with up to 14.0 g K m Ϫ2 (Belesky and Wilkinson, 1983) regression equations starting with a second order polynomial model. Growth of FloraDwarf was highly responsive to photoperiod, in that and up to 41.9 g m Ϫ2 (Cripps et al., 1989). 'Tifton 44' decreased daylengths reduced growth. No growth differences were increased shoot and root growth in response to 14.0 g found in Tifdwarf due to daylength. Growth increased in response to K m Ϫ2 (Belesky and Wilkinson, 1983). N in both cultivars, while growth response to K varied by cultivar. Differential responses also have been reported for Both cultivars accumulated higher levels of TNC under short day quality in response to N and K. Quality and density in conditions, with higher levels in FloraDwarf. Nitrogen fertilization 'Tifway' increased up to 20 g N m Ϫ2 yr Ϫ1 (Johnson et al., reduced TNC levels in FloraDwarf under short days and in Tifdwarf 1987) and promoted early spring green up in 'Tifgreen' under long days, while K fertilization reduced TNC levels in Tifdwarf (Reeves et al., 1970). Potassium fertilization has inunder short days. Quality scores in both cultivars increased in response creased resistance to cultural stresses such as wear, soil to N under long days, and in response to both N and K under short compaction, and cold temperatures (Carrow et al., 1987; days. Results of these studies indicated that growth, TNC accumulation, and quality differed due to cultivar, photoperiod, and rates of Juska and Murray, 1974). N and K.

Seashore paspalum (Paspalum vaginatum Swartz) displays wide intraspecific diversity and exhibits tolerance to numerous abiotic stresses. In addition, comparatively low fertility requirements and high quality growth characteristics of many ecotypes render this grass a prospective candidate for use on golf courses, athletic fields, and landscaped areas in warm climates worldwide. The objectives of this research were to evaluate the relative growth, quality, and wear tolerance of seashore paspalum and bermudagrass. This research was conducted in two consecutive field trials during 1997 under wear and non-wear conditions on seven seashore paspalum ecotypes and three hybrid bermudagrass (Cynodon dactylon L. × C. transvaalensis Burtt-Davy) cultivars established on a native Appling sandy clay loam (clayey, kaolinitic, thermic typic Kanhapluduit) at the University Georgia Experiment Station at Griffin, GA. We found that two paspalum ecotypes, Temple 1 and SIPV-2 , ranked as high or higher than 'Tifway' and 'Tifsport' for visual quality, shoot density, shoot growth, and amount of verdure tissue under non-wear conditions. In addition, these two paspalum ecotypes showed the most favorable spectral reflectance data responses, indicating greatest utilization of intercepted light, and also showed rates of recovery from wear which were equal to or greater than those of the bermudagrass entries. Paspalum ecotypes Temple 1 and SIPV-2 appear to be suitable for use in areas where a high quality, traffic-tolerant turfgrass is required. Paspalum ecotypes with lower shoot densities were less wear tolerant.