Lucerne production following residual herbicides used in northern cropping systems

Abstract

Lucerne ( Medicago sativa L.) is finding an increasing role in dryland farming systems of the grain region of northern New South Wales and Queensland as a ley legume to improve soil fertility, grain yield and quality. Residual herbicides play an essential role in weed management in crop rotations in this region, although their persistent residues may damage the susceptible crops sown following their use. Experiments were conducted on two soil types to test the effects of application time of residual herbicides (winter and summer) on the survival and production of lucerne sown in the following autumn/winter.
The effect of the herbicides on initial seedling growth varied with herbicide, rate of application and soil type. Seedling establishment was not affected. Reduced seedling vigour and phototoxicity were evident in some treatments. However, irrespective of seedling response, the lucerne recovered with no subsequent reduction in dry matter production at any site at the first cut taken 5 months after sowing.