Optimising pasture production to minimise weed growth

Abstract

Weeds are part of any land based production system and need to be managed appropriately to minimise their negative impact on economic returns. Too frequently herbicides are used routinely to cure the weed problem without examining the underlying cause of the problem. Routine herbicide use poses risks to the environment and damages New Zealand's 'Clean and Green' image, therefore alternative weed management strategies need to be considered. In pasture based systems, ensuring that the forage species are in prime condition all year round is the method of choice to reduce weed problems to sub-economic levels. Forage grasses are very competitive, so much so that they often prevent significant contributions from companion species like white clover. In an experiment Californian thistle was grown in pasture maintained at two different height ranges. Maintaining a longer pasture significantly reduced Californian thistle shoot production, while not affecting total forage production. It is concluded that maintaining longer pasture residuals not only slightly increased pasture production, it also minimised weed problems and should therefore be the choice weed control strategy for pastoral farmers, wherever possible. Keywords: Californian thistle, grazing, pasture management, weed management