Developments with seed drill coulters for direct drilling

Abstract

Abstract When overdrilling into established pasture, the application of paraquat plus dicamba, or glyphosate, sprayed simultaneously in bands on the drilled rows, was both a feasible and an effective way of suppressing competition from resident plant species. Pilot experiments highlighted the need for precise control of nozzle height and suggested preferences for placement of the nozzles in relation to both chisel and triple disc coulter assemblies. Experiments in the Bay of Plenty, Waikato, and Manawatu on paspalum-, browntop-, and clover-dominant swards suggested that in all these pastures, paraquat + dicamba produced a more rapid and complete suppression of resident vegetation within the bands than did glyphosate. Both herbicides applied in bands were better than not spraying, but suffered in the longer term in comparison with blanket spraying. In the Waikato there was an advantage with paraquat using a chisel coulter assembly in comparison with a triple disc coulter assembly but no logical explanation can be advanced to explain this effect.