Wednesday, November 15, 2006 - 8:30 AM

Comparison of Improved, Novel and Default Species Pastures using a Production Sensitivity Index.

Vern Baron, Agriculture and Agri-Food Canada, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada, John A. Basarab, Alberta Algriculture Food and Rural Development, 6000 C&E Trail, Lacombe, AB T4L 1W1, Canada, and F. Craig Stevenson, F. C. Stevenson, Statistician, 142 Rodgers Road, Saskatoon, SK S7K 3T6, Canada.

Performance of an “improved” (meadow bromegrass), a “novel” annual (spring oat and winter triticale) and “default” species (quackgrass, smooth bromegrass and Kentucky bluegrass) pastures, managed for intensive stocker systems, were compared over 7 yr. at Lacombe, AB using a production sensitivity index.  Cross-bred heifers were rotationally grazed within 0.9 ha paddocks, replicated three times at variable stocking rates using the “Put and Take” method.  The objective was to determine if the improved species and novel pastures had more potential than the typical low-cost default pasture-types, when managed optimally.    The index estimates were the average beef production over all treatments for each year (n = 7).  A linear regression was conducted with the index as the independent variable and the raw data for measured variables, including beef production as the dependent variables.  Regression coefficients among treatments were tested in a mixed model where treatments were considered fixed and years random effects. Also, regression coefficients were tested for significance from zero for each treatment.  Treatment means were estimated at the minimum, average and maximum index positions based on the regression between index and the respective response variables. Means were compared using LSD0.05 generated from the mixed model regression analyses.  These positions generally, but not necessarily, corresponded to years of lowest, average and highest rainfall. Regression coefficients over the index were greater for improved than other pastures for pasture days, stocking rate and carrying capacity and greater than novel, but not default for beef ha-1. Improved had greater values for stocking rate and carrying capacity than other pastures at average and maximum index positions and had 14, 19 and 22% more beef ha-1 than default at minimum, average and maximum positions than default, but was not significantly different. Novel was never superior to default.