Strains of Blue Grama and Sideoats Grama Evaluated for the Southern Great Plains

Abstract

Strains of blue grama and sideoats grama were evaluated for forage yield and quality under dryland conditions on the Southern Great Plains. In vitro dry matter digestibility (IVDMD) and crude protein content were determined as measures of forage quality. WW 65 blue grama was the leading strain of blue grama for every parameter measured, but it was significantly greater than the other blue grama strains only in IVDMD. Although no strain of sideoats grama proved superior in forage yield, PMT 328 sideoats grama was highest in crude protein content and was signiflcantly greater than all other strains of sideoats grama in IVDMD. WW 65 blue grama and PMT 328 sideoats grama exhibited superior forage quality with at least comparable forage yield to the other strains of blue grama and sideoats grama, respectively. Underground irrigation water in a large portion of the Southern Great Plains is now declining. Many soils in this area are highly susceptible to wind erosion when intensively cultivated under dryland conditions. Re-establishment of permanent vegetation is an obvious alternative for these Authors are former graduate research assistant and associate professor emeritus, respectively, Texas Tech University and Texas Agricultural Experiment Station, Lubbock, Texas. Presently the senior author is a graduate research assistant of Texas AM Mcllvain and Shoop 1960). Potential production of these species under irrigation and fertilization was determined on the High Plains of Texas (Jaynes and Hunter 1961; Lehman et al. 1969). Holscher (1945), Newell et al. (1962), Dwyer (1971), and Willard and Schuster (1971) reported on the performance of certain strains of blue grama and sideoats grama grown under dryland conditions. Animal performance was evaluated from grazing studies with these grasses on the Southern Great Plains at Woodward, Okla., (Mcllvain and Shoop 1960) and at Amarillo, Texas (Whitfield et al. 1949). These studies indicate that forage production of blue grama and sideoats grama was generally comparable to that of other adapted species in favorable years with greater tolerance to grazing in less favorable years. Several improved strains of these species have been developed and are now available. This study was conducted to evaluate currently available selections and experimental strains of blue grama and sideJOURNAL OF RANGE MANAGEMENT 33(5), September 1980 381 This content downloaded from 157.55.39.231 on Wed, 05 Oct 2016 04:33:38 UTC All use subject to http://about.jstor.org/terms oats grama for dryland production in the Southern Great Plains. Forage yield and forage quality were determined on the strains evaluated. Materials and Methods The field study was on an established plant materials nursery at the Texas Agricultural Experiment Station north of Lubbock, Texas. The grasses were seeded in 1973. Four strains of blue grama and eight strains of sideoats grama were replicated three times in a randomized complete block design. Grasses evaluated included commercially available and experimental strains (Table I). Strains of blue grama used were common blue grama and the experimental selections PMT 697, PMT 1221, and WW 65. Strains of sideoats grama were as follows: Premier, El Reno, Vaughan, Uvalde, and the experimental selections Block E, PMT470, PMT201,and PMT328. Eachentryoccupieda3X4m plot. Plantings were in rows with each plot being four rows wide. Herbage yields were determined by clipping during the 1976 and 1977 growing seasons. A section 60 cm long in each of the two inside rows in each plot was clipped. Forage from the two rows was composited into one sample per replication. Both species were harvested on the same dates throughout the growing season. Harvests were made immediately after all plots of blue grama had attained a minimum height of 15 cm and all plots of sideoats grama had attained a minimum of 20 cm. Blue grama was clipped at a 7.5 cm stubble height while sideoats grama was clipped at a 10 cm stubble height. The material was dried at 50? C for 72 hours then weighed. Samples taken in 1976 were then ground to pass through a 0.5 mm screen in preparation for further analysis. In vitro dry matter digestibility (IVDMD) and crude protein determinations were used as measures of quality of the total available forage. These analyses were made on the plant material harvested during the 1976 growing season. The IVDMD procedure used was the Tilley and Terry (1963) two-stage method with modifications as described by Teel (1970). Protein determinations were made by the Kjeldahl procedure (Association of Official Agricultural Chemists 1965). Forage yield, percent IVDMD, and percent crude protein were statistically analyzed, and the parameters with significant differences among selections were compared using Duncan's multiple range test. Results and Discussion The frequent harvests in 1976 made it possible to deterrable 2. In vitro dry matter digestibility, crude protein, and yield of blue grama strains on the Southern High Plains. Weighted Weighted mean' mean crude IVDMD protein Yield Yield2 Strain (1976) (1976) (1976) (1977) % %0 kg/ ha kg/ ha WW 65 61.54 a3 16.68 a 2752 a 2254 a PMT 1221 60.06 b 15.24 a 2463 a 2094 a Common 59.63 b 16.09 a 2226 a 1689 a PMT 697 59.03 b 16.12 a 2668 a 1701 a 'Weighted means were calculated by multiplying the percent IVDMD and crude protein, respectively, of each harvest by the yield for that harvest, totaling the products, and dividing this total by the total yield for the year. 2Total yield from harvests on May I1, June 3, June 27, Aug. 8, Sept. 12, and Oct. 21. 3Means within each column followed by the same letter are not significantly different at the .05 level. mine the quality of forage available throughout the growing season as environmental conditions changed. Higher stubble heights than usual were maintained to compensate for the effects of frequent clipping on plant vigor. Forage harvested in this study was undoubtedly affected by the interaction of clipping frequency and stubble height. As shown by Holscher (1945) and Crowston and Goetz (1976), higher yields would be expected with less frequent clipping.