Evaluation of the Forage-disk Method in Mixed-grass Rangelands of Kansas

Abstract

The forage disk meter, a double sampling device used to predict forage biomass, has been used extensively on improved pastures, but its use on rangelands has not been investigated thoroughly. Efficiency of the forage disk meter was investigated in predicting yields of forage biomass on different range sites in western Kansas. Using least squares regression methods, resting heights (forage bulk) and dry matter yields were used to calibrate the disk meter for each site and sampling date. Highly significant regressions (P<0.0001) were obtained on all the shortgrass sites, where several factors that had unfavorable effects on the regression relationship between forage bulk and forage biomass were not apparent. These factors, although not quantified, included accumulation of litter, microrelief, lodged vegetation, and presence of broadleaf species. Regression coefficients (b) and intercepts (a) varied between sites and dates, thus the forage disk meter should be calibrated for every range site. If a forage disk meter is calibrated for a specific range site, regression coefficients and intercepts might not differ from year to year if grazing pressure and species composition are temporally consistent, which implies that recalibration might be unnecessary. The forage disk meter was useful as a double sampling device on range sites dominated by shortgrasses, but its use was limited on areas dominated by annual forbs or midgrasses.