Effect of timing of glyphosate and 2,2-DPA application on establishment of surface-sown pasture species

Abstract

In two experiments on unploughed hill country near Turondale, New South Wales, the effects were examined of applying glyphosate and 2,2-DPA before and after the autumn break and at various intervals before sowing on the establishment of surface-sown Medicago sativa, Trifolium subterraneum, Dactylis glomerata and Phalaris tuberosa. Good control of resident species was obtained by applying herbicides from 10 to 30 days after autumn rain had promoted germination of winter annuals; poor control resulted if herbicides were applied before the autumn break. Glyphosate was more efficient in controlling resident species than 2,2-DPA. The establishment of all species except subterranean clover depended on good control of the resident plants. It was also necessary to have an adequate period between spraying and sowing to allow the residual herbicide to dissipate; 10 days was sufficient for the grasses, 20 days for lucerne and longer for subterranean clover. A 4.5 kg a.e. ha-1 rate of glyphosata had a more serious residual effect than a 1.5 kg a.e. ha-1 rate or the 2,2-DPA treatment. Results showed that good establishment of surface-sown legumes and grasses can be obtained by applying 0.5 to 1.5 kg a.e. ha-1 of glyphosate, or 8.7 kg a.e. ha-1 of 2,2-DPA, 10 to 30 days after autumn rain and then sowing 10 to 20 days later.