BUCKING THE trend towards continuous cropping, West Australian growers are increasing livestock numbers and including a pasture,phase as one of their main strategies for tackling herbicide resistance, according to a recent survey by the Liebe Group (see table).
While a pasture phase may not always be profitable compared to crops, most of the 38 growers and all 12 agronomists who took part in the survey highlighted the importance of a pasture phase in getting on top of weeds and minimising the threat of herbicide resistance.
Growers who took part in the survey had all shown an interest in weed management by choosing to be part of a rapid-adoption weed management project supported by growers and the Federal Government through the GRDC.
When asked to rank the weed that posed the greatest threat to their wheat crops, growers rated annual ryegrass as the number one enemy followed by wild radish, bromegrass, wild oats, doublegee and Paterson's Curse. Agronomists responded with the same ranking except that they rated wild radish as a slightly greater problem than annual ryegrass.
Other best-bet anti-weed strategies
In addition to adopting a pasture phase, growers and agronomists shared some common thoughts on the top five other integrated weed management (IWM) practices (see table). While growers rated a high crop-seeding rate as the top IWM practice, for agronomists growing a hay or silage crop was number one. Growers also rated highly the practice of spraytopping pasture with a non-selective herbicide, but this was not an option on the questionnaire provided to agronomists.
Although agronomists rated the hay/silage, green or brown manure and chaff carts as three of the most effective IWM practices, they also indicated that growers were not most likely to adopt these approaches due to cost implications.
Five growers who took part in the survey said they planned to maintain close to 100 per cent crop and they will need a strict IWM program to do so.
The agronomists demonstrated their view of the importance of a pasture phase by nominating rotations that average 73 per cent crop. All of the agronomists also responded positively to the idea that new technology plus IWM plus a non-crop phase in the rotation are necessary to keep on top of resistant weeds.
Mr Stuart McAlpine 08 9664 2082
Rating, ranking and adoption of various IWM practices
|Integrated weed management (IWM) practice||Agronomists' rating of IWM practice (score out of 10)||Agronomists top five ranked practices (1=highest ranked)||Likely grower adoption (top five practices as ranked by agronomists) (1=highest ranked)||Growers' top five adopted practices (1=highest ranked)|
|Autumn tickle to stimulate weed germination||6.2|
|Cultivation to kill weeds||7.4|
|Deliberately delay seeding for two weeks or more after your normal seeding time for weed control purposes||7.7|
|Use glyphosate and paraquat as a 'double-knock' for ryegrass control (not tank mix)||8.1||4||4||2|
|Early sowing of grassy paddocks to increase crop competition with weeds||5.1|
|Sowing cereal crops with a high crop-seeding rate to increase competition with weeds||7.5||2||1|
|Grow a green or brown manure crop||8.3||3|
|Grow a hay or silage crop||8.7||1|
|Crop topping a crop using glyphosate or paraquat prior to harvesting||8.5||2||1||5|
|A chaff cart or seed catcher to collect weed seeds at harvest||7.8||5|
|Spray-top pasture with non-selective herbicide||4|
|Burn crop stubble (whole paddock)||7.7||5||3|
|Burn crop stubble (header windrows only)||7.0||3|
|GMO crop (e.g. Roundup Ready®)||4.1|