Development and evaluation of a standardised means for estimating herbage mass of dairy pastures using the rising plate meter.

Abstract

Calibration data for the rising plate meter (RPM) collected from four locations and spanning a period of 10 years (1988-1998) were used to develop a pooled standard set of RPM calibrations to be used to estimate herbage mass of dairy pastures across a number of dairying regions. When evaluated in a farmlet study run over a 2-year period, the standard RPM calibration gave similar estimates of average farm cover, pre and postgrazing herbage mass and consumed DM, as herbage mass estimates calculated from RPM measurements calibrated to the local pasture on each assessment day. Compared with visual estimations, the standard RPM calibration underestimated pre-grazing herbage mass, average farm cover and the amount of pasture consumed, and overestimated post-grazing herbage mass. Reasons for these differences are discussed and an alternative approach to using the RPM for on-farm pasture assessment is presented. Standardised, onfarm herbage mass estimates may be possible using the RPM and standard calibrations to calibrate visual estimations prior to visually assessing pasture across the whole farm. Such a standardised pasture assessment method would assist the grazing management of dairy pastures across a number of New Zealand dairying districts. Keywords: average farm cover, dairy-grazing management, pasture growth, post-grazing herbage mass, pre-grazing herbage mass, rising plate meter