Farm Table says:
The take home messages from this GRDC funded research are below. Please access the full paper via the link below for methodology, references, acknowledgements and discussion.
Take home messages from the paper include:
- The response of weed density to delayed sowing is influenced not just by the weather conditions, but also by the seed dormancy attributes of the weed populations. Less dormant weed populations tend to emerge quickly after the opening rains, and they can be managed well by moderate delays in sowing. However, much longer delays in sowing would be needed to reduce infestations of highly dormant weed populations.
- At Washpool in 2019, a three-week delay in sowing had no impact on in-crop ryegrass density. In contrast, delayed sowing at Minnipa in 2018 caused a significant reduction in ryegrass density in wheat. Similarly, in-crop density of brome grass was also significantly reduced by the delayed sowing at Marrabel in 2018.
- A lower weed density after delayed sowing does not always reduce weed seed set. For example, late sown wheat at Washpool had more than double the ryegrass head number than in the early sown crop. Colder soil temperatures in later sown crops can reduce crop vigour, which allows weeds to thrive.
- Delayed sowing in June resulted in a significant yield penalty across all these trials. A decision to delay sowing to manage weeds needs to be considered very carefully.
- Higher crop seeding rates appear to consistently improve weed suppression especially in the later sown crops.