Crop weeds: stop weed seed set

Page last updated: Wednesday, 17 February 2021 - 10:41am

Please note: This content may be out of date and is currently under review.

Mechanical topping or targeted grazing

Targeted grazing using sheep

Another tactic to control weeds is mechanical topping, which refers to slashing or mowing activities late in the season to prevent development of weed seeds. It can be used as an alternative to spray-topping, particularly where resistance to knockdown herbicides is a problem. However, it is slower and more expensive than spray-topping and the plants have a greater chance of regrowing to produce seeds. Mechanical topping can alternatively be achieved by grazing, provided that a sufficient number of dry sheep are available.

Spray-topping compared with mechanical management and targeted grazing for seed set control in pastures.

Table 1 Spray-topping compared with mechanical management and targeted grazing for seed set control in pastures
Tactic	Advantages	Disadvantages
Spray-topping using paraquat or glyphosate	quick economical pasture can be grazed afterwards (check withholding period) efficacy on target weed can be greater than 90%	desirable species can be affected (glyphosate can be more of a problem than paraquat) if timing is poor
Mechanical topping	non-selective can be used on organic farms used in conjunction with grazing	time consuming plants often regrow, especially if rain falls soon after cutting can have profound effect on species balance
Targeted grazing	non-chemical option for organic farms small positive income stream from wool production	large number of dry sheep needed difficult to treat large areas stock may increase density of some species (like silver grass) can have profound effect on species balance the grazing technique required to alter pasture grass composition generally involves placing a lot of stress on the sheep involved and stressed animals will exhibit reduced performance unless sufficient grazing pressure is applied, sheep will ignore the targeted weed species

Topics

Contact information

Alex Douglas

+61 (0)8 9821 3246

Email Alex Douglas

You are here

Crop weeds: stop weed seed set

Mechanical topping or targeted grazing

Topics

Contact information