SOME OBSERVATIONS OF PASTURE MANAGEMENT EFFECTS ON GRASS GRUB, PORINA AND EARTHWORM POPULATIONS

Abstract

Changes in management practices will automatically alter the equilibrium between organisms making up the pasture ecosystem with results not necessarily beneficial to the economic production of the system. Indications of these interactions were observed and monitored in pasture management pasture species trials at Palmerston North. Grass grub attack developed more rapidly, and populations reached higher levels under rotational grazing than set stocking. Porina caterpillar populations tended to show the reverse with higher populations under set stocking than rotational grazing. Earthworm populations were higher under set stocking with a greater proportion of burrowing types, compared to rotational grazing which favoured more of the surface feeding species. These changes are discussed in terms of differences in pasture structure and defoliation patterns affecting microclimate and food supplies for the survival of these organisms. Keywords: Pasture management, rotational grazing, set stocktng, grass grub, porina, earthworms, pasture structure, pasture biomass.