Adaptation of forage bermudagrasses [Cynodon dactylon (L.) Pers.] to the Texas High Plains grown under saline and limited irrigation conditions
Marsalis, Mark A
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Information is limited concerning adaptation of forage bermudagrasses [Cynodon dactylon (L.) Pers.] to the Texas High Plains. Due to increasing scarcity of Ogallala Aquifer water and increased use of secondary water sources for irrigation, greenhouse and small plot field trials were conducted to evaluate bermudagrass as a potential component in forage-livestock systems using limited or saline irrigation. In a greenhouse experiment, salinity tolerance of 'Macho', an experimental variety, was tested over 56 d with a range of salinity from 1.7 to 90.0 dS m-1, imposed as NaCl and CaCl2 (1:1) in a complete nutrient solution. Plants were grown in sand in 2-L pots in a completely randomized design with six replications of each treatment. Plants were harvested at 28 and 56 d. Although plants survived salinity levels as high as 38 dS m-1 over 56 d, growth of Macho was reduced by 50% at 12 dS m-1. Productivity at 12 dSm-1 and higher would limit usefulness of Macho bermudagrass. In a second greenhouse trial, relative salinity tolerances of 'Tifton 85', 'Coastal', and Macho bermudagrasses were evaluated during 63 d. Plants were grown in sand in 2-L pots using a completely randomized design. Treatments (NaCl: CaCl2; 1:1) ranging from 1.4 to 37.5 dS m-1 were imposed in a nutrient solution. Upper limit of salinity was based on results from the pilot greenhouse experiment. Biomass was harvested at three, 21-d intervals. Biomass reductions of 75% occurred at 27.0, 27.0, 17.0; 27.0, 19.0, 17.0; and 19.0, 14.0, 14.0 dS m-1 for Tifton 85, Macho, and Coastal, respectively, at each 21-d harvest. After 63 d, Tifton 85 and Macho survived salinity levels up to 27.0 dS m'\ whereas Coastal survived up to 19.0 dS m-1. Productivity and nutritive value among eight sprigged and four seeded forage bermudagrasses were tested during 2002 and 2003 in small plot trials at three locations in Texas: (1) New Deal; 12 varieties with limited irrigation (313 mm total annual) with water from the Ogallala Aquifer; (2) Posey; 5 varieties surface irrigated with industrial wastewater; and (3) Spraberry; 5 varieties surface irrigated with municipal effluent water. For locations 2 and 3, water was applied at disposal rates and Sporobolus virginicus (L.) Kunth., a salt tolerant perennial grass, was tested in addition to bermudagrasses. Experimental design was a randomized complete block at each location. Forage mass was determined by clipped quadrates every 28 d during the growing seasons of 2 yr following the establishment yr to estimate production. Mean seasonal yield of Tifton 85 was greater than other varieties (P < 0.05) with aquifer water (20.4 Mg ha-1) and industrial wastewater (17.1 Mg ha"') but did not differ from Coastal with municipal effluent water. In vitro dry matter disappearance (IVDMD) for Tifton 85 (63%) was higher (P < 0.05) than other varieties at each location. Growth of Tifton 85 was delayed early in spring compared with others tested. Mean seasonal yields and IVDMD did not differ among sprigged and seeded varieties. Adaptation of S. virginicus to more northern areas of the Texas High Plains is questionable due to loss of stands at Posey, but is more promising in southern regions grown with moderately saline water. Bermudagrass appears adapted to environmental conditions of the Texas High Plains under varying irrigated conditions, but more research is needed to determine suitability of these grasses for use in long-term grazing and haying systems.