Two approaches, irrigation with impaired waters, and use of subsurface drip irrigation, have been identifi ed as strategies to reduce the use of potable water for landscape irrigation. A study was conducted at New Mexico State University in Las Cruces in 2008 and 2009 to investigate the establishment of Princess 77 bermudagrass [Cynodon dactylon (L.)] and Sea Spray seashore paspalum [Paspalum vaginatum (Sw.)] seeded in March (dormant) or June (traditional). Th e grasses were irrigated at 98% reference evapotranspiration with saline [electrical conductivity (EC) = 2.3 dS m -1 ] or potable (EC = 0.6 dS m -1 ) water from either a sprinkler or a subsurfacedrip system. Establishment did not diff er between the two grasses regardless of seeding date, irrigation type, or water quality. Generally, grasses that were seeded dormant reached 75% cover faster and exhibited greatest ground cover at the end of both growing seasons. When data were averaged over water qualities and seeding dates, sprinkler irrigation resulted in greater ground cover (90% in 2008 and 92% in 2009) than drip irrigation (58% in 2008 and 80% in 2009) at the end of both research periods. Highest EC levels at rootzone depths of 0 to 10 cm were observed in November 2009 on plots drip irrigated with saline water, averaging 4.4 dS m -1 compared to 2.3 dS m -1 on sprinkler irrigated plots. Our results indicate that when using subsurface-drip irrigation, early seeding is required to successfully establish seashore paspalum and bermudagrass from seed in one growing season.New Mexico State Univ., Las Cruces, NM 88003.

A study was conducted at New Mexico State University in Las Cruces, NM, from 2010 to 2012 to investigate the effects of deficit irrigation on bermudagrass (Cynodon dactylon L.) cultivar Princess 77 and seashore paspalum (Paspalum vaginatum Swartz) cultivar Sea Spray treated with either soil surfactants [Revolution (modified methyl capped block copolymer) or Dispatch (alkyl polyglucoside blended with a straight block copolymer)] or a plant growth regulator [Trinexapac‐ethyl (TE); 4‐(cyclopropylhydroxymethylene)‐3,5‐dioxocyclohexanecarboxylic acid]. Irrigation was applied daily at 50% reference evapotranspiration from either a sprinkler or a subsurface drip system with either potable (electrical conductivity [EC] = 0.6 dS m−1) or saline (2.3 dS m−1) water. Normalized Difference Vegetation Index (NDVI) and visual ratings were determined monthly to assess stand quality and turf stress. Princess 77 treated with TE showed the highest quality and the highest NDVI (0.655) on 10 out of 15 sampling dates. Positive effects of TE applications were also observed on Sea Spray quality, NDVI, and fall color retention. Subsurface drip irrigation resulted in higher quality and NDVI during the third year of the study when compared with sprinkler irrigation. Salinity buildup in the root zone did not negatively affect visual quality of the tested warm‐season species. Generally, sprinkler irrigation system and turf treated with Revolution promoted higher water distribution uniformity (lower standard deviations) than the other treatments. Further research is needed to investigate if greater drought tolerance of subsurface drip–irrigated turf is the result of increased water‐use efficiency due to altered root morphology.

A study was conducted in New Mexico from 2005 to 2007 to investigate the effects of two potable water‐saving strategies, irrigating with saline water and using subsurface systems, on changes in rootzone salinity and quality of nine warm‐season turfgrasses. Plots were irrigated using either sprinklers or subsurface drip with water of 1 of 3 salinity levels (0.6, 2.0, and 3.5 dS m−1). Plots were rated monthly for quality during the growing seasons and bi‐annually for spring and fall color. Soil samples were collected bi‐annually (June and November) and analyzed for electrical conductivity (EC), Na, and sodium adsorption ratio (SAR) at depths of 0 to 20 and 50 to 60 cm. Electrical conductivity and Na values in 0 to 20 cm peaked in June of 2005 and 2006 and dropped to lower levels after the summer rainy season. With the exception of moderately saline irrigated plots in 2005, summer EC did not differ between drip and sprinkler irrigated plots for any of the three water qualities. Electrical conductivity, Na, and SAR at a rootzone depth of 0 to 20 cm were highest in June 2006 reaching 4.7 dS m−1, 1024 mg L−1, and 16.1, respectively. For most of the grasses tested, EC, Na, or SAR values showed no significant relationship with turf quality. Drip irrigation resulted in earlier green‐up than sprinkler irrigation but had no effect on summer quality or fall color retention. Most of the warm season grasses included in this study maintained an acceptable quality level when drip‐irrigated with saline water.

A primary concern in managing warm‐season turfgrasses within the transition zone is the lengthy dormant period, during which these swards lack green color. The objectives of this study were to determine the effects of three N fertilization schedules on spring green‐up and fall color retention of bermudagrass [Cynodon dactylon (L.) Pers.] and seashore paspalum (Paspalum vaginatum Sw.). A field trial was performed at the agricultural experimental farm of Padova University (northeastern Italy). Bermudagrass cultivars Princess‐77, Riviera, SWI 1014, and Yukon and seashore paspalum ‘Sea Spray’ were compared under three N fertilization schedules: (i) 6.7 g N m−2 on 15 May, 15 June, and 15 August, (ii) 5 g N m−2 on 15 May, 15 June, 15 August, and 15 October, and (iii) 4 g N m−2 on 15 May, 15 June, 15 August, 15 September, and 15 October. Spring green‐up was estimated weekly as a percent green turfgrass coverage from 15 March to 15 June of 2010 and 2011. Fall color retention was visually rated from September to November of 2010 and 2011. Sea Spray seashore paspalum had later spring green‐up and better fall color than the bermudagrass cultivars, which differed widely in terms of spring green‐up and fall color retention. Fall‐applied N enhanced green‐up of all the grasses tested and extended fall color retention of bermudagrass cultivars. This study revealed that protracting applications of N fertilizer until late season may improve quality performance of warm‐season grasses without increasing annual N applied.

ABSTRACTe limitations of the conventional visual rating system used to assess turfgrass quality include its subjective nature and the need for properly trained observers who can discern di erences among treatments or turfgrass varieties. e objective of our study was to investigate if digital image analysis (DIA) and spectral re ectance [normalized di erence vegetative index (NDVI)] can be used to evaluate turfgrass varieties. Trials were established at New Mexico State University and visual quality ratings, digital images, and NDVI were collected monthly on three warm-season and three cool-season variety trials and on one cool-season and one warm-season mixed species trial. Correlations among quality, NDVI, dark green color index (DGCI) and percent green cover (PCov) were computed. Multiple regression was used to determine if combining NDVI and DIA improved the association between visual turfgrass quality and other variables. uality was most strongly associated with NDVI (R 2 ranging from 0.37 to 0.65) for most datasets. Additionally, multiple linear regressions identi ed NDVI as the variable a ecting a higher change in R 2 when entered to the model than either DGCI or PCov. Visual quality had a weaker association with sampling date than did NDVI or DGCI, which indicates that NDVI may track quality changes more reliably over time. However, a stronger association between variety and visual quality than between variety and NDVI or DGCI indicates that a visual assessment detects varietal di erences better. erefore, it is questionable whether visual assessments can be replaced by NDVI or DIA to characterize the aesthetic appeal of turfgrasses accurately.

Information is needed to determine if adequate turf quality can be maintained over several growing seasons when grasses are irrigated from the subsurface. A study was conducted in Las Cruces, NM, from 2005 to 2008 to investigate the performance of one bermudagrass blend and ten warm‐season species and varieties under subsurface drip irrigation. Plots were mowed at 7.5 cm, irrigated at 90% ETo and fertilized to prevent nutrient stress. Visual ratings were taken monthly from March 2005 to June 2008 to determine turf quality, spring green up, and fall color retention. Normalized Difference Vegetation Indices (NDVI) were collected monthly from March 2007 through June 2008. When quality data were averaged over the 4 years, seashore paspalum ‘SeaDwarf,’ ‘Sea Spray,’ and zoysiagrass ‘De Anza’ had the best performance and sideoats grama ‘Vaughn’ the worst during the summer. The study showed that inland saltgrass ‘A138’ achieved the fastest spring green‐up, whereas De Anza was the slowest. SeaDwarf stayed green the longest in the fall, while Vaughn was the first cultivar to lose color and go dormant. The correlation between visual turfgrass quality and NDVI was significant (P < 0.001) but not very strong, yielding a correlation coefficient of r = 0.54.

n the United States, turfgrass represents a signifi cant component of urban landscapes. These turfgrass areas include residential lawns, commercial plantings, public roadside areas, parks, athletic fi elds, cemeteries, and golf courses. Using high-resolution photographs in 13 major urban centers, Milesi et al. (2005) estimated a total turfgrass area in the United States of 163,812 km 2 and suggested that turfgrass represents the single largest irrigated crop in the United States, an area three times larger than that of irrigated corn. Although not all of this turfgrass is subject to high-intensity irrigation management, the majority of it, with the exception of turfgrass grown in wet humid regions, receives at least supplemental water during the peak summer months. However, in the arid West, turfgrass cannot exist in an acceptable state without regular supplemental water. For example, in Las Vegas, NV, rainfall is typically less than 12 cm yr −1 , which means that turfgrass grown under golf-course conditions would receive more than 95% of its water requirement via irrigation. On the other hand, in Mobile AL, the National Weather Service (NOAA, National Climatic Data Center, 2009) reported an average rainfall for the period 1996-2008 of 15 ± 4.6 cm mo −1 , which would suggest that only high-maintenance turfgrass might require supplemental water during drier periods. The amount of irrigation required by turfgrass varies from region to region on the basis of climate, species, water quality, irrigation management, cultural management, and soil type. Christians and Engelke (1994) described the general bioclimatic zones for turfgrass in the United States. Such zones were separated according to their suitability for cool-season and warm-season species. The authors noted that many turfgrass species are being grown in areas for which they are not well suited or environmentally adapted. To compensate for that use, environmental modifi cations must be made, such as signifi cant increases in irrigation, fertilization, and pesticide applications. Smaller, regional zones are

Warm-season grasses are not widely accepted in Mediterranean countries because they lose color during the winter months. A study was conducted at the University of Padova (Padova, Italy) to determine whether fall and spring water-soluble carbohydrate (WSC) content in stolons of seeded bermudagrass cultivars (Cynodon dactylon) influenced spring green-up in the first year of establishment. Nine bermudagrass cultivars (La Paloma, Mohawk, NuMex Sahara, Princess 77, Riviera, SR 9554, Barbados, Contessa, and Yukon) were seeded in July 2005, and dry weight and WSC content in stolons were measured in Fall 2005 and again in Spring 2006. The percentage of green cover and days needed to achieve 80% green cover (D80) were regressed against November and March values of stolon dry weight and WSC content to determine if they were good predictors of D80. ‘Yukon’ showed earliest spring green-up by end of April, and ‘Princess 77’ and ‘Riviera’ were slowest, needing 43 to 46 days more than ‘Yukon’ to reach D80. There was a significant inverse relationship between November (r2 = 0.57) and March (r2 = 0.77) WSC content in stolons and D80 for all nine bermudagrass cultivars. These results suggest that bermudagrass cultivars with high WSC in stolons recover more rapidly from dormancy during establishment than those with low WSC content.