Pasture utilisation in hill country 1. Influence of grazing duration and land contour

Abstract

Precise control of pasture utilisation in hill country is difficult because of differences in feed availability, and animal grazing requirements and preferences. The influence of varying grazing duration and stock densities, and the ratio of easy to steep land area on pasture utilisation patterns was assessed during late summer and mid winter with mobs of mixed-age ewes grazing land typical of North Island hill country. Demand for pasture exceeded supply during the grazing period and pasture allowances were similar. Mean pasture disappearance rates (DM per ewe grazing day) were greater with longer duration/lower stock density combinations. Consequently for these combinations, low pasture DM levels were achieved relatively earlier, ewes grazed at minimum accessible pasture levels for longer time periods, and final utilisation was more uniform. Disappearance rates of pasture were greater on easy compared with steep land, these differences being enhanced with long grazing durations, and/or during the early stages of grazing. Short duration/high density grazings reduced preferential grazing of easy land when animal choice was greatest. Removal of pasture on easy land was increased, and that on steep land decreased when either land strata was the minor component of the paddock. Efficient utilisation of potentially high productive easy land would be best achieved with a low ratio of easy to steep land. Initial DM levels of pasture communities had minimal effect in modifying relationships between pasture utilisation, grazing duration, land class, and plant type.