In a mixed farming operation, winter cleaning of pasture is a valuable tool which utilises non-selective herbicides to control grass weeds. Winter cleaning involves using products such as Gramoxone (paraquat), Simazine, plus where required Jaguar (bromoxynil & diflufenican), to remove or suppress annual weeds in lucerne based pastures.
Benefits to be gained from winter cleaning pasture include:
- Reduction in the population of herbicide resistant weeds.
- Removing problem grasses from pastures to be grazed by lambs during spring.
- Reduction of grass weeds prior to the cropping phase.
- Reduction in cereal diseases such as Take-all and Crown Rot.
- Increased Nitrogen fixation.
- Prolonged life of the pasture.
- Increased clover seed set
- Conservation of moisture for use by lucerne and clover during spring.
Historically there has been a reluctance to winter clean. A common argument being “I can’t afford to lose the feed”. This is very short term thinking and failure to undertake winter cleaning for this reason, prevents growers from capturing possibly the two largest synergies that exist between pastures and crops, being the control of grass weeds (which host disease) and the fixation of Nitrogen. Whilst there is a short term loss of feed, the benefits far out way the losses. With planning and management, grazing crops or productive perennial grass pastures can be utilised to fill the feed gap during the pasture recovery period.
The success of winter cleaning can vary greatly with seasonal conditions. It also requires preparation and planning to achieve good results. Following are some guidelines that will lead to improved results from winter cleaning:
Ideal timing is 6-8 weeks after the autumn break, whilst weeds are small but once clover is well established.
Pastures need to be grazed short and to be free of dry residue from the previous spring.
Good soil moisture is beneficial to the result.
Simazine is taken into the weeds through the roots; therefore rainfall soon after application leads to improved results.
Paraquat is a contact herbicide, so high water rates (100L/ha) leads to more consistent results.
Heavy grazing post–application can improve results.
An adequate population of clover and perennial pasture species having good nutrition, must be present to take the place of weeds.
With a good early break and ideal growing conditions this year, many pastures are in a less than ideal condition to winter clean. However, astute managers have been able to target specific paddocks by using high stocking rates and rotational grazing to achieve good results.
Consideration needs to be given to alternative control measures such as spray topping, or for smaller areas cutting silage or hay from pastures that have high grass weed pressure, which are unable to be winter cleaned.
The ideal timing for winter cleaning is two years prior to commencement of the cropping phase.
Experience suggests that if a pasture can be winter cleaned for two consecutive years during a pasture phase, or if winter cleaning can be used strategically with spray topping, hay or silage, grass weeds can be significantly reduced or even eliminated. Consistent effective results from winter cleaning requires planning and grazing management for several months prior to the time of application. They also require a positive attitude, plus a willingness to make it work in order to obtain the benefits.