Grains Research and Development

Date: 01.11.2002

About shielded sprayers by John Rochecouste and Michael Burgis, Conservation Farmers Inc.

CFI trial cooperators busy controlling weeds in cotton before the next cloud burst, November 2001.

DOES A shielded sprayer fit in the northern grain industry?

Quite simply, yes it does! In fact shielded sprayers are already in use by some growers, because they provide farm managers with alternative options for weed control.

A shielded sprayer allows more management options. The big concern is crop safety. Everyone worries about it, and there have been plenty of bad experiences to make growers very cautious. Interestingly the benefits have been worthwhile enough to make many growers and contractors persevere.

Following are some reasons farmers have given for the use of shielded sprayers.

  • The difficulties of managing pre-emergent herbicides under dry climatic conditions. Often the herbicide is locked into the dry surface layer of the soil, with weed germination coming from subsoil moisture. Where perhaps there were inadequate post-emergent herbicides for the weed spectrum, shielded sprayers went from being a band-aid treatment to a regular tool.
  • Shifts in the weed spectrum meant new problem weeds were developing that could not be controlled by registered post-emergent herbicides. Using a shielded sprayer increased the options of available herbicides.
  • The familiarity, wide weed spectrum and price of glyphosate meant that it was a product that many were looking to introduce in-crop.
  • Many crop pre-emergent herbicides were being applied in bands as a cost saving and the inter-row weeds cultivated. However, in dry seasons the option to spray inter-row and conserve moisture became a worthwhile economic consideration.
  • Disease management of soil-borne pathogens is another consideration for certain situations. The movement of Fusarium spp. through soil disturbance is being managed in some cotton paddocks by spraying rather then cultivating. Shielded sprayers can provide options for managing crown rot (Fusarium pseudograminearum) and root lesion nematode-infected paddocks. Hygiene considerations for ground-engaging tools are critical to prevent possible transfer to other paddocks or farms.
  • The timing of weed control in overly wet conditions sometimes means that the first machine that can get on the paddock is the sprayer, not the cultivator.