THE advantages of early seeding and crop competition were firmly on the agenda at the WA No-Tillage Farmers Association's (WANTFA) harvest weed seed management trial last week.
The trial aimed to explore the efficacy of both herbicide choice and harvest weed seed management techniques on ryegrass control for dry and delayed sown crops.
WANTFA executive director David Minkey said the trial was multi-faceted and wasn't simply subjected to a one-off treatment.
In recent years an increased number of growers sowed crops before the break of the season to make the most of timing, yield and profit advantages.
But the risks associated with weed management due to the absence of a knockdown herbicide and the potential damaging effects on the performance of pre-emergent herbicides in dry soil, made growers question which was the best herbicide option for them.
The site trialled three herbicides including trifluralin and two new herbicides, Sakura and Boxer Gold, both of which had incorporation needs less than trifluralin and were thought to be more suitable to the WANTFA trial site.
The trial also tested the effectiveness of the Harrington Seed Destructor (HSD) which mitigated the need for burning residue and fitted well within high-residue no-till farming systems.
Dr Minkey said interestingly the dry sown wheat with a pre-emergent herbicide grew less ryegrass than the delayed seeding trial with a knockdown.
"The reason for that is because the trials emerged in early May with warm temperatures," he said.
"The wheat sky-rocketed and out-competed the weeds whereas in the delayed seeding, it got cold and wet and the wheat came out of the ground pretty slowly.
"There was some really strong interaction between pre-emergent herbicides and crop competition.
"Dry seeding worked really well except in the plots with trifluralin.
"Whereas in other trial sites with sandier soil types trifluralin worked really well.
"The number one message for growers is that early seeding and crop competition is the key to better ryegrass control."
Dr Minkey said the trial was extremely time appropriate because modelling figures showed the last decade, more so than any other, provided a large number of WA growers lots of opportunity to dry seed.
"The biggest issue growers face is weed management because they're not using a knockdown herbicide in many cases," Dr Minkey said.
"The lack of the use of a knockdown throughout the central and northern Wheatbelt in particular is huge and there's even a growing tendency for it in the Great Southern depending on recent yearly rainfall figures.
"Some growers like Corrigin's Lance Turner dry seed their entire cropping program so it's becoming very popular."
Dr Minkey said one of the central issues surrounding dry seeding was the control of ryegrass populations.
He said the WANTFA trial looked at dry seeding and which pre-emergent herbicides worked best under dry seeding conditions.
"This year the HSD didn't work that well," he said.
"Because we had a drought last year not all the ryegrass got up out of the ground so there was still a huge seed bank that carried over to this year.
"We only got about a 30 per cent reduction in ryegrass in the part of the trial where the HSD was used."
But Dr Minkey said this season would be the perfect year to put the HSD to the test.
Higher rainfall figures throughout much of the State meant most ryegrass seed banks in the Wheatbelt germinated and the HSD would be able to destroy that seed before it fell to the ground.
