• Evaluation of a single probe capacitance meter for estimating herbage yield

      Currie, P. O.; Hilken, T. O.; White, R. S. (Society for Range Management, 1987-11-01)
      A single probe electronic capacitance meter for estimating herbage yields was field tested on 2 western wheatgrass (Pascopyrum smithii (Rydb.) Löve), a blue grama (Bouteloua gracilis (H.B.K.) Lag. ex Griffiths), crested wheatgrass (Agropyron cristatum (L.) Gaertn.), and Russian wildrye (Psathrostachys juncea (Fisch.) Nevski) stands in the Northern Great Plains. This single probe meter is lightweight, portable, and allows the user to estimate yields of single plants to determine productivity of individual species. Linear regression equations were fitted between probe readings and the green and dry weight of forage clipped from individual plants within a $78.5-cm2 circular plot. An overall coefficient of determination (r2) of 0.50 was obtained with linear relationships being statistically significant between the probe readings and green and dry weight of forage for all regressions (P=0.10). Considering the regression estimates for r2, standard error of the estimate and F values, the best model fit occurred in the western wheatgrass and crested wheatgrass stands. Presence of a litter mat in 1 western wheatgrass stand had little influence on the precision of the instrument, but phenology of the plants strongly influenced meter readings. Therefore, regression lines within a species could not be pooled across all sampling dates. Comparing yields of individual species from the small plots of the single probe meter to yields from a larger, $1,858-cm2 rectangular plot estimated with a multi-probe capacitance meter showed comparisons were not statistically different 50% of the time. A sample size of approximately 150 plots per species was required for each sample period for the single probe meter.
    • Factors affecting dietary preferences for genotypes of a hybrid wheatgrass

      Truscott, D. R.; Currie, P. O. (Society for Range Management, 1987-11-01)
      Interspecific hybridization of grasses represents a valuable plant breeding procedure for developing new species with superior grazing value for livestock. Evaluations were made of the hybrid cross between quackgrass (Elytrigia repens [L.] Beauv.) × bluebunch wheatgrass (Pseudoroegneria spicata [Pursh.] Scribn and Smith) to determine how animal preferences for these hybrids were influenced by grazing season and year. Significant differences in the preference shown by steers as measured by bite counts in 1981 and percent utilization (P<0.01) in 1982 existed among the 46 clonal lines for each of the 2 successive years. Preference rankings for lines selected the first year were not identical to those selected a second year although lines with high preference rankings the first year were generally preferred the second year. A clonal line, designated line 30, was most preferred in 7 of 8 subtrials in 1981 and ranked in the top 3 preferred plants in all trials in 1982. There was a 4-week period in early summer when preference differences were minimal. It was attributed to the abundant regrowth on all lines at this time and was found to have a significant (P<0.01) effect on steers' dietary choices.
    • Selective control of annual bromes in perennial grass stands

      Currie, P. O.; Volesky, J. D.; Hilken, T. O.; White, R. S. (Society for Range Management, 1987-11-01)
      Three soil-active herbicides: atrazine [6-chloro-N-ethyl]-N1-(1-methyethyl)-1,3,5-triazine-2,4-diamine]; propham (1-methylethyl phenyl carbamate); and pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] were applied in the fall, postemergence to annual bromegrasses at 2 rates. These herbicides were evaluated for their efficacy in selective control of cheatgrass (Bromus tectorum L.) and Japanese brome (Bromus japonicus Thunb.) in perennial stands of crested wheatgrass (Agropyron cristatum [L.] Gaertn.), pubescent wheatgrass (Thinopyrum intermedium Host), Russian wildrye (Psathrostachys juncea [Fisch.] Nevski), and western wheatgrass (Pascopyrum smithii (Rydb.) Löve) and blue grama (Bouteloua gracilis) [H.B.K.] Lag. Ex Griffiths. Yields of annual bromegrasses and perennial grasses and crude protein (CP), phosphorus and total nonstructural carbohydrate (TNC) content of perennial grasses were measured 2 consecutive years after the single herbicide application. Yields of annual bromegrasses from the 3 herbicide treatments averaged 91 and 47% less than those of the control the first and second year posttreatment, respectively. Pronamide provided substantially better control the second year posttreatment than the other 2 herbicides. Yields of perennial grasses in the majority of the herbicide treatment-study site combinations were significantly increased the first year posttreatment (P<0.10). Crude protein of perennial grasses was increased in the atrazine treatment. Atrazine at 0.6 kg/ha was the most cost-effective herbicide for decreasing competition of annual bromegrasses and increasing yield of perennial grasses.