Evaluation of techniques for estimating the yield of irrigated pastures intensively grazed by dairy cows. 2. The rising plate meter

Abstract

A semi-automatic rising plate meter, the Ellinbank Pasture Meter (EPM) was used to estimate herbage yields of the three most common types of irrigated pasture intensively grazed by dairy cows in northern Victoria. While there were only small differences in precision between the pasture types, yields of pre-grazed pastures were measured more precisely than yields of post-grazed pastures. The EPM also estimated pre-grazing yield more precisely than a visual assessment technique, while the two techniques were similar for estimating post-grazed herbage. A number of factors, including dry matter content of the herbage, botanical composition, season, and lodging due to trampling were shown to influence pre- and post-grazing regressions. It was concluded that pooled regressions were therefore unsuitable for research purposes unless the pooling was for a relatively short period only. Pre- and post-grazing data can be pooled for periods of up to two months to allow the estimation of pasture growth rates at various points of time between grazings. An alternative method of obtaining yield estimates has been proposed in which it is not necessary to develop a regression. This method relies on cutting quadrats in each plot that are representative of the yield and composition of the plot. While this method can circumvent some of the problems associated with the factors that influence the yield-height relationship, severe lodging due to trampling of the sward may preclude the use of the EPM regardless of method.