Fresh, senesced, and decaying pine needles from Pinus halepensis were evaluated for their allelopathic potential on Festuca arundinacea, Cynodon dactylon and the biosensor plants Avena sativa and Lemna minor through in vivo and in vitro studies. The in vivo study was performed in growth chambers, using 6, 12, and 18 g of pine needle tissue mixed with screened perlite as a substrate. The effects of the different pine needle types were evaluated by determining the total root length, total root surface, root dry weight, total shoot length, total shoot surface, and shoot dry weight. The in vitro study was performed in Petri dishes where seeds from each species were subjected to an increasing concentration of pine needle extract. The extracts were obtained from pine needle ground tissue that was diluted with water and either shacked at room temperature or placed in water bath at 40 °C for 24 h. The evaluation of the allelopathic potential was performed with the determination of radicle length. The allelopathic potential of the pine needle tissues was confirmed with bioassays using oat (A. sativa) and duckweed (L. minor). The results strongly suggested the allelopathic potential of the pine needle tissue, being more pronounced in the fresh, moderate in the senesced, and low in the decaying pine needles. The allelopathic substances were species-specific, and the inhibition resistance of the species tested followed the order F. arundinacea > C. dactylon > A. sativa. The inhibition of the L. minor suggested that the water soluble phytotoxic compounds were inhibitors of Photosystem II.
Panayiotis A. Nektarios, Garyfalia Economou, and Christos Avgoulas
Michael S. Harrell and Grady L. Miller
The benefits of composted yard waste applied as a mulch were demonstrated in a field study at two locations and supporting greenhouse research. Compost was applied to eroded roadside slopes of about 12° and 27° to determine the influence on soil displacement and establishment and/or enhancement of permanent roadside vegetation. Treatments consisted of compost rates of 5 cm and planted with asiastic jasmine (Trachelopermum asiaticum), 5 and 10 cm, seeded with 110 or 220 kg·ha–1 80:20 bahiagrass (Paspalum notatum Flugge): bermudagrass (Cynodon dactylon L.) seed mix by weight, straw erosion control mats, and bahiagrass sod. Compost treatments effectively controlled soil displacement regardless of compost rate or seeding with turfgrass at both locations. Effects on roadside vegetation and visual quality varied with location. Asiatic jasmine did not establish at either site. Compost mulch applications increased total vegetation, turfgrass density, and quality at the site with 27° slope and 4% initial soil organic matter content, but resulted in a decline in cover at the site with a 12° slope and <1% organic matter content. Compost mulch can effectively prevent soil displacement from roadside slopes, but may not promote establishment or enhancement of permanent vegetative cover.
Jayne M. Zajicek, Nowell J. Adams, and Shelley A. McReynolds
Landscape plantings have been designed traditionally using aesthetic criteria with minimal consideration given to water requirements. The primary objective of this research was to develop quantitative information on water use of plant communities conventionally used in urban landscapes. Pots of Photinia × Fraseri (photinia Fraseri), Lagerstroemia indica 'Carolina Beauty' (crape myrtle), or Ligustrum japonicum (wax leaf ligustrum) were transplanted from 3.8 l into 75.7 l pots with either Stenotaphrum secundatum 'Texas Common' (St. Augustinegrass), Cynodon dactylon × C. transvallensis 'Tiffway' (bermudagrass), Trachelospermum asiaticum (Asiatic jasmine), or left with bare soil. Whole community water use was measured gravimetrically. In addition, sap flow rates were recorded for shrub species with stem flow gauges. Sap flow measurements were correlated to whole community water use recorded during the same time intervals. Whole community water use differed due to the groundcover component; bermudagrass, Asiatic jasmine, and bare soil communities used less water than St. Augustinegrass communities. Differences were also noted in stomatal conductance and leaf water potential among the species.
Michael D. Richardson, John McCalla, Tina Buxton, and Filippo Lulli
Many early spring bulb species are naturally found in grassy areas such as meadows or lawns. However, few studies have been conducted to define this concept in maintained lawns, especially warm-season lawns such as zoysiagrass (Zoysia japonica) or bermudagrass (Cynodon dactylon). Four early spring bulb species, including two crocus species (Crocus tommasinianus ‘Ruby Giant’ and Crocus chrysanthus ‘Goldilocks’), reticulated iris (Iris reticulata ‘Cantab’), and snowdrop (Galanthus elwesii) were established in a zoysiagrass lawn site in Fall 2010. In Spring 2011 and 2012, five common preemergence herbicides used on lawns were applied across the plots to determine phytotoxicity. In addition, mowing treatments were started on plots at two timings (15 Mar. and 15 Apr.) to determine how mowing might affect survival and performance of the bulb species. Early performance was good for all bulb species and greater than 50% flower production was observed in the first spring (2011) after planting. However, in the subsequent 3 years (2012–14), the only species that persisted and continued to flower adequately each spring was ‘Ruby Giant’ crocus. Herbicides and mowing did not affect bulb survival or performance in the trial, suggesting that typical lawn management practices will not be deleterious to the bulbs. These results demonstrate that early spring bulbs may be incorporated into dormant, warm-season lawns, but species and cultivar selection will be crucial for long-term performance.
Chanjin Chung, Tracy A. Boyer, Marco Palma, and Monika Ghimire
This study estimates potential economic impacts of developing drought- and shade-tolerant bermudagrass (Cynodon dactylon) turf varieties in five southern states: Texas, Florida, Georgia, Oklahoma, and North Carolina. First, estimates are provided for the market-level crop values of the newly developed two varieties for each state. Then, an economic impact analysis is conducted using an input–output model to assess additional output values (direct, indirect, and induced impacts), value added, and employment due to the new varieties. Our results indicate that the two new varieties would offer significant economic impacts for the central and eastern regions of the United States. Under the assumption of full adoption, the two new products would generate $142.4 million of total output, $91.3 million of value added, and 1258 new jobs. When a lower adoption rate is assumed at 20%, the expected economic impacts would generate $28.5 million of output, $18.3 million of value added, and 252 jobs in the region. Our findings quantify the potential economic benefits of development and adoption of new turfgrass varieties with desirable attributes for residential use. The findings suggest that researchers, producers, and policymakers continue their efforts to meet consumers’ needs, and in doing so, they will also reduce municipal water consumption in regions suited to bermudagrass varieties.
Grady L. Miller and Adam Thomas
Application of nutrients to correct nutrient deficiencies in turfgrasses are often based on tissue analysis. Previous research has indicated that near infrared reflectance spectroscopy (NIRS) may be useful in tissue nutrient concentration determination since it requires minimum sample preparation and has been a reliable predictor of N concentration. The objective of this study was to evaluate the reliability of NIRS in determining P, K, Ca, and Mg concentrations in bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy]. Tissue samples were collected from Florida golf courses, representing different cultivars grown under various conditions and fertilizer regimes. Tissue samples were analyzed using NIRS and traditional wet chemistry (Mehlich-1 extracts analyzed using inductively coupled argon spectrophotometer) before results were statistically compared. Results from wet chemistry analysis averaged 15% lower than those obtained from NIRS. Although results for certain cultivars and elements were positively correlated (`Tifdwarf' Ca, r 2 = 0.72; P < 0.01), precision across all cultivars and nutrients was not sufficient (accounted for only 26% of variability) to indicate that NIRS would be an effective management tool for the elements evaluated in this study.
Marco Schiavon, Brent D. Barnes, David A. Shaw, J. Michael Henry, and James H. Baird
Replacing cool-season turf with more drought and heat tolerant warm-season turfgrass species is a viable water conservation strategy in climates where water resources and precipitation are limited. Field studies were conducted in Riverside and Irvine, CA, to investigate three methods (scalping, eradication with a nonselective herbicide, planting into existing turf) of converting an existing tall fescue (Festuca arundinacea) sward to warm-season turf. Cultivars established vegetatively by plugging were ‘De Anza’ hybrid zoysiagrass [Zoysia matrella × (Z. japonica × Z. tenuifolia)], ‘Palmetto’ st. augustinegrass (Stenotaphrum secundatum), ‘Tifsport’ hybrid bermudagrass (Cynodon dactylon × C. transvaalensis), ‘Sea Spray’ seashore paspalum (Paspalum vaginatum), and ‘UC Verde’ buffalograss (Buchloe dactyloides). Cultivars established from seeds were ‘Princess-77’ bermudagrass (C. dactylon) and ‘Sea Spray’ seashore paspalum. Neither scalping nor planting into existing tall fescue were effective conversion strategies, as none of the warm-season turfgrasses reached 50% groundcover within 1 year of planting. All of the species except for st. augustinegrass reached a higher percentage of groundcover at the end of the study when glyphosate herbicide was applied to tall fescue before propagation compared with the other conversion strategies. Bermudagrass and seashore paspalum established from seeds and hybrid bermudagrass from plugs provided the best overall establishment with 97%, 93%, and 85% groundcover, respectively, when glyphosate was used before establishment. Quality of seeded cultivars matched or exceeded that of cultivars established vegetatively by plugging. These results suggest that eradication of tall fescue turf followed by establishment of warm-season turf from seeds is the best and easiest turf conversion strategy.
Michael T. Deaton and David W. Williams
The use of seeded bermudagrasses (Cynodon dactylon) is increasing as athletic field and golf course turf. Anecdotal evidence indicates probable and important differences in germination rates among cultivars when established in late spring or early summer. Germination studies were completed in May 2011 in the Turfgrass Science Laboratory at the University of Kentucky on 19 commercially available seeded bermudagrass cultivars. Evaluations for germination rate and total germination under varying temperature regimes representing 20-year average day/night temperatures for seeding times from 15 May to 1 Aug. were conducted to quantify any differences in germination characteristics among cultivars as affected by temperature. There were highly significant differences (P < 0.0001) among cultivars in germination rate and total germination when grown under 20-year average day/night temperatures. The cultivars Casino Royale and Riviera consistently represented the fastest/slowest to germinate and highest/lowest total seeds germinated across all temperature regimes, respectively. Significant differences (P < 0.0001) were also observed within cultivars for total germination across the temperature regimes tested. The average temperatures of 15 May and 1 Aug. represented slowest/fastest to germinate and lowest/highest total seeds germinated across all temperature regimes, respectively.
John M. Kauffman, John C. Sorochan, and Dean A. Kopsell
Thatch-mat and organic matter (OM) accumulation near the putting green soil surface impacts soil physical properties and turf performance. Excessive thatch and OM can encumber infiltration of water and oxygen into the soil profile and slow drainage of excess water away from the putting surface. Proper sampling of thatch-mat depths and OM contents is vital for management of putting green turf; therefore, a study was performed in Knoxville, TN, to derive proper sampling procedures of these important parameters using ‘TifEagle’ and ‘Champion’ bermudagrass (Cynodon dactylon × C. transvaalensis), ‘SeaDwarf’ seashore paspalum (Paspalum vaginatum), and ‘Diamond’ zoysiagrass (Zoysia matrella). ‘TifEagle’ and ‘Champion’ accumulated thatch-mat to a greater depth than ‘SeaDwarf’ and ‘Diamond’. However, ‘SeaDwarf’ had a higher OM content than ‘Diamond’ and both had higher OM contents than ‘TifEagle’ and ‘Champion’. Data generated from sampling procedures indicate that previous studies often undersampled plots for thatch-mat depth; however, previous sampling procedures have not traditionally undersampled plots for OM. Data in this study provide a range of confidence and minimum detectable difference levels which may allow future researchers to more accurately sample ‘TifEagle’, ‘Champion’, ‘SeaDwarf’, and ‘Diamond’ putting green plots for thatch-mat depth and OM content.
Hassan Salehi, Zahra Seddighi, Alexandra N. Kravchenko, and Mariam B. Sticklen
Bermudagrass (Cynodon L.C. Rich.) is grown on more than 4 million ha in the southern United States. The black cutworm (Agrotis ipsilon Hufnagel) is the most commonly encountered pest of bermudagrass, especially on golf course greens. Developing insect-resistant cultivars is a very desirable substitute, both environmentally and economically, to using current synthetic pesticides. Here we report, for the first time, Agrobacterium-mediated transformation of `Arizona Common' common bermudagrass [Cynodon dactylon (L.) Pers.] with the Bacillus thuringiensis Berliner cry1Ac gene encoding an endotoxin active against black cutworm. Mature seeds were used for producing embryogenic callus, and calli were transformed with a plasmid containing a synthetic cry1Ac and the kanamycin resistance (nptII) genes. Putative transgenic calli and plantlets were selected on media containing 100 and 50 mg·L-1 G418, respectively. RNA-blot analysis of PCR-positive lines revealed the expression of the cry1Ac transgene in three out of five putative transgenic lines. The larvae fed on transgenic plant leaves experienced highly significant (over 80%) mortality.