We conducted several experiments to determine the best system for production of spring cabbage (Brassica oleracea L. Capitata group) with conservation tillage (CT) in the southern plains of the United States. Rye (Secale cereale L.) was selected as the best cover crop to cover the soil in a short time. Raised beds were formed in the fall and planted with rye. With most studies, the rye was allowed to remain on the soil surface rather than being tilled into the soil. Planting densities, rates of nitrogen fertilizer, and herbicide materials were evaluated to determine the best system for cabbage production. In each study, various cover crop practices were compared with bare soil production systems. Soil erosion was reduced by the use of rye cover crops. Cabbage was produced in the CT system, but cabbage yields were higher in bare soil plots than in the rye-covered plots. We are also in the process of developing a system of CT that involves permanent bermudagrass [Cynodon dactylon (L.) Pers.] pastures and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. This system allows both crops to be grown simultaneously on the same land.
Warren Roberts, James Shrefler, James Duthie, Jonathan Edelson, Bob Cartwright, and Nancy Roe
Alex J. Lindsey, Joseph DeFrank, and Zhiqiang Cheng
The use of nonpotable water for irrigation on various sport venues has led to an increased use of seashore paspalum (Paspalum vaginatum) turf in Hawaii. An ongoing challenge many seashore paspalum turf managers struggle with is bermudagrass (Cynodon dactylon) infestations. Herbicide efficacy studies were conducted at the Hoakalei Country Club [‘SeaDwarf’ seashore paspalum (fairway cut)] and the Magoon Research Station [‘SeaStar’ seashore paspalum (grown in container)] on the island of Oahu in Hawaii. Spray applications of the herbicides mesotrione, topramezone, metribuzin, and ethofumesate were evaluated alone and in tank mixtures for bermudagrass suppression and seashore paspalum injury. At the Hoakalei Country Club, maximum bermudagrass injury with minimal seashore paspalum discoloration was obtained with tank mixes of mesotrione (0.06 lb/acre) + metribuzin (0.19 lb/acre) + ethofumesate (1.00 lb/acre) and topramezone (0.02 lb/acre) + metribuzin (0.19 lb/acre) + ethofumesate (1.00 lb/acre). Unacceptable seashore paspalum turf injury was obtained in all treatments that did not include metribuzin. At the Magoon Research Station, maximum selective bermudagrass suppression was achieved with tank mixes of topramezone (0.01 lb/acre) + ethofumesate (1.00 lb/acre) and topramezone (0.01 lb/acre) + metribuzin (0.09 lb/acre) + ethofumesate (1.00 lb/acre). The addition of metribuzin and/or ethofumesate to the tank mix safened (reduced turf discoloration) seashore paspalum to topramezone or mesotrione foliar bleaching. Tank mixes of mesotrione, topramezone, metribuzin, and ethofumesate have the potential for bermudagrass suppression and control of other grassy weeds in seashore paspalum turf.
Yaling Qian and Jack D. Fry
Greenhouse studies were conducted on three warm-season turfgrasses, `Midlawn' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy], `Prairie' buffalograss [Buchloe dactyloides (Nutt.) Engelm.], and `Meyer' zoysiagrass (Zoysia japonica Steud.), and a cool-season turfgrass, `Mustang' tall fescue (Festuca arundinacea Schreb.) to determine 1) water relations and drought tolerance characteristics by subjecting container-grown grasses to drought and 2) potential relationships between osmotic adjustment (OA) and turf recovery after severe drought. Tall fescue was clipped at 6.3 cm once weekly, whereas warm-season grasses were clipped at 4.5 cm twice weekly. The threshold volumetric soil water content (SWC) at which a sharp decline in leaf water potential (ψL) occurred was higher for tall fescue than for warm-season grasses. Buffalograss exhibited the lowest and tall fescue exhibited the highest reduction in leaf pressure potential (ψP) per unit decline in ψL during dry down. Ranking of grasses for magnitude of OA was buffalograss (0.84 MPa) = zoysiagrass (0.77 MPa) > bermudagrass (0.60 MPa) > tall fescue (0.34 MPa). Grass coverage 2 weeks after irrigation was resumed was correlated positively with magnitude of OA (r = 0.66, P < 0.05).
Jinmin Fu, Jack Fry, and Bingru Huang
Water requirements for `Meyer' zoysiagrass (Zoysia japonica Steud., hereafter referred to as zoysia), `Midlawn' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy, hereafter referred to as bermuda], `Falcon II' tall fescue (Festuca arundinacea Schreb.) and `Brilliant' kentucky bluegrass (Poa pratensis L., hereafter referred to as bluegrass) were evaluated under a mobile rainout shelter at deficit irrigation levels of 20% to 100% of actual evapotranspiration (ETa), applied twice weekly, between June and September 2001 and 2002. Soil was a river-deposited silt loam (fine, montmorillonitic, mesic Aquic Arquidolls). Minimum annual irrigation amounts required to maintain quality ranged from 244 mm for bermuda to 552 mm for bluegrass. Turfgrass species and respective irrigation levels (% of ETa) at which season-long acceptable turf quality was maintained in each year were bluegrass, 100% (evaluated 2001 only); tall fescue, 60% in 2001 and 80% in 2002; bermuda, 60% in both years; and zoysia, 80% in both years. A landscape manager who could tolerate one week of less-than-acceptable quality could have irrigated tall fescue at 40% ETa (224 mm) in 2001 and 60% ETa (359 mm) in 2002. Likewise, bermuda exhibited unacceptable quality on only one September rating date when irrigated at 40% ETa (163 mm) in 2001. Bermuda was able to tolerate a lower leaf relative water content (LRWC) and higher level of leaf electrolyte leakage (EL) compared to other grasses before quality declined to an unacceptable level.
E.A. Guertal and J.N. Shaw
A 3-year study was conducted in Auburn, Ala., on an established hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy `Tifway'] stand maintained at a 2.54-cm mowing height. Treatments were level of soil traffic applied via a weighted golf cart to produce turf and soil that received varying amounts of traffic. Dormant bermudagrass was overseeded with perennial ryegrass (Lolium perenne L.) each October, which remained until May of each year. Spectral data were collected monthly using a multispectral radiometer. Percent reflectance data were acquired over 512 discrete wavelengths in visible (VIS) and near-infrared (NIR) ranges. Quarterly data collection included soil penetrometer and bulk density measurements to a depth of 15 cm. After 2 years of traffic, both soil penetrometer and bulk density data indicated statistically significant increases in soil compaction. In general, as traffic increased there were also increases in percent reflectance in the VIS range. Data were subject to temporal variation, however, as values changed with the date of sample collection. The NIR reflectance data provided little consistent correlation to measurements of soil compaction. Use of NIR and VIS radiometry to evaluate turf stress showed some potential, but temporal variation must be considered.
M.L. Elliott, E.A. Guertal, and H.D. Skipper
The rhizospheres of creeping bentgrass (Agrostis palustris Huds.) and hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) putting greens were sampled quarterly for 4 years. Six bacterial groups, including total aerobic bacteria, fluorescent pseudomonads, actinomycetes, Gram-negative bacteria, Gram-positive bacteria, and heat-tolerant bacteria, were enumerated. The putting greens were located in four geographic locations (bentgrass in Alabama and North Carolina; bermudagrass in Florida and South Carolina) and were maintained according to local maintenance practices. Significant effects were observed for sampling date, turfgrass species and location, with most variation due to either turfgrass species or location. Bentgrass roots had significantly greater numbers of fluorescent pseudomonads than bermudagrass roots, while bermudagrass roots had significantly greater numbers of Gram-positive bacteria, actinomycetes and heat-tolerant bacteria. The North Carolina or South Carolina locations always had the greatest number of bacteria in each bacterial group. For most sampling dates in all four locations and both turfgrass species, there was a minimum, per gram dry root, of 107 CFUs enumerated on the total aerobic bacterial medium and a minimum of 105 CFUs enumerated on the actinomycete bacterial medium. Thus, it appears that in the southeastern U.S. there are large numbers of culturable bacteria in putting green rhizospheres that are relatively stable over time and geographic location.
Panayiotis A. Nektarios, Garyfalia Economou, and Christos Avgoulas
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.
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.
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.