Search

This study was conducted to develop a calibration for paddock mean falling plate meter height (PH), herbage density (HD) and herbage mass (HM) in rotationally stocked pastures under different fertility treatments and to determine if there was a seasonal or treatment effect on the calibration. Accurate, rapid measurement of HM is needed in pasture research and for on-farm pasture budgeting. Four rotationally stocked pastures were sampled for PH using a standardized falling plate meter. Pastures were predominantly orchardgrass, bluegrass, and white clover. Fertility treatments were poultry litter at 4,480 kg/ha/year, poultry litter at 8,960 kg/ha/year, lime and phosphorous as needed based on soil test, and lime only as needed based on soil test. Pastures were walked on established transects and 15 paired PH and HM samples were taken at random and clipped to ground level. For each data pair, HD was calculated by dividing HM by PH. Paddock means for PH, HD and HM were calculated for each paddock and sampling date. Paddocks were sampled just before grazing over a 3 year period as follows (month/number of sampling periods): May/16, June/8, July/5, August/7, September/4, October/11, and November/8. Regressions of paddock mean HD and paddock mean HM as functions of PH were calculated using all paddock sampling dates and fertility treatments. The plate meter calibration regression for HD based on PH was: HD = 264 - 6.6 PH; R2 = 0.29; SDreg = 42. Regression coefficients were significant (P<0.001). Estimating mean pasture HM as the product of PH times HD resulted in a second order function without an intercept and was: HM = 264 PH - 6.6 PH2. Compared to the clipped HM measured this model had an R2 = 0.93; SDreg = 687. Analysis of variance of regression residuals found no significant effect of season or treatment on the accuracy of HD and HM estimates. This method provides one calibration that applies across seasons and fertility treatment for pastures of similar botanical composition and under the same defoliation management. [ABSTRACT FROM AUTHOR]