The 2014 season has been a rollercoaster to say the least, and the ride isn’t over yet. Harvest for some Wimmera and Mallee farmers is still in full swing, whilst the header is back in the shed for others. Rainfall throughout the region in recent weeks, although an interruption for harvest it is still positive for storing moisture.
Unfortunately though, it has germinated summer weeds, so even though the header is still going, it is important to act on weeds sucking up valuable moisture. BCG research shows controlling summer weeds increases seasonal water use efficiency by 60 percent on average.
Benefits of effective summer weed control
Good summer weed management not only conserves soil moisture, but also available nitrogen. It improves crop establishment and reduces issues with weed vectored pests and diseases.
BCG has done multiple research trials on summer weed control with a focus on moisture conservation. These trials have left no doubt in our minds the value in controlling summer weeds in relation to increasing yields of the following crop and return on investment.
In the short term, a summer weed burden contributed to a 50% loss in production the following year whilst in the long term a 1t/ha loss of production was experienced (see BCG 2008 Season Research Results pp. 122).
Considerations of summer spraying
Hot and dry conditions mean that there is only a narrow window for optimal spray timing. This is because if weeds are under heat or drought stress the efficacy of the spray application may be reduced. Ensure droplet survival and penetration of target by spraying in the right conditions.
Product selection, rates and timing
As always, product selection, rates and timing are vital to ensure an effective spray. The most effective timing is two to four weeks post germination. Regardless of water quality, it is recommended to add ammonium sulphate and a penetrant during summer, and if water quality is an issue use adjuvants. If appropriate, the use of residuals will put you on the front foot with subsequent germinations.
Spray set up and operation
Setting up your sprayer and correct operation is also key. Good coverage may require higher water rates in summer (however, this may require a compromise if it is a dry season). Optimal spray conditions are at temperatures less than 28°C, a Delta T of 2-10 and wind speeds between 3-15 km/h.
If conditions deteriorate throughout the operation – it is better to stop and wait for optimal conditions than waste time and money. Travelling less than 15km/hr will assist in reducing issues of weeds surviving due to dust in the wheel tracks.
Finally, it may pay to enlist help, to not miss the opportunity to spray, or have to spray at a later growth stage decreasing efficacy.
For further information on getting your summer spray right see BCG 2006 Season Research Results – Keeping summer weed control cost effective pp. 110-117.
A difficult season means that cash flow is tough, but this also means that it is vital to maximise opportunities going into 2015, particularly to conserve moisture. The rainfall may have provided you with the opportunity to get on the front foot with summer weed control. Following the guidelines and getting in early will make all the difference.
Links to resources:
Keeping summer weed control cost effective
BCG 2006 Season Research Results (110-117)
