Producers can effectively keep weeds out of their lentil crops using steel between the rows and mechanical tools
As some weeds gain resistance to Group 2 herbicides, several techniques are being developed to control weeds in lentils without the use of herbicides.
To address this, a research study comparing different mechanical weed removal methods in lentil crops is showing promise.
Steve Shirtliffe and his team from the University of Saskatchewan analyzed three in-crop mechanical weed control methods: tine harrows, rotary hoe and inter-row tillage.
The four-year test plot study compared the implements individually and looked at which ones work best together, even though they have separate niches.
“All in-crop mechanical weed control methods reduced weed biomass,” Shirtliffe said at CropSphere Jan. 9.
“Any of them alone did a decent job of weed control. We were getting at least a 50 percent weed biomass reduction by using anything.”
He said the rotary hoe works well controlling weeds at pre-emergence to early cotyledon.
The harrow can be used at pre-emergence to small weed seedlings, but there are issues with crop tolerance.
Inter-row tillage is an effective tool for digging up weeds but needs to wait until crop rows are visually established in the five to 10 node stage so as not to till them up. The usual spacing is 12 inches, but some organic producers are as narrow as 7.5 inches.
Shirtliffe said using the mechanical weed implements at different stages in the crop produced the highest success.
“In the real world, it probably depends upon the exact weather conditions and everything (else), but certainly the one consistent winner was using an early rotary hoeing that would control the weeds just when they’re first emerging to get it as clean as possible and then coming back later with inter-row tillage to get those larger weeds that are in between the rows,” he said.
Best combinations increased seed yield approximately 70 percent and reduced weed biomass by about 80 percent.
In a separate but limited, one site year study, the researchers had some success controlling kochia in lentil crops using a rotary hoe.
“It’s just one site, so I don’t want to emphasize it too much,” he said.
“I think what we can take out of that is fall applied Edge (ethalflurulin) can be an effective control for kochia and that rotary hoeing can work on kochia as well.”
Shirtliffe said future plans for mechanical weed control research is being extended to other crops with Australia providing leading research into “harvest weed seed management.”
“In other words, to look at managing the weed seeds going back into your soil as a management tool, and we’ve started to look at that in two ways,” he said.
One method uses clippers that skim over the tops of lentil crops and cuts the weed flowers, particularly in wild mustard by cutting them off in the newly developing pods.
“We found it can be quite effective in reducing weed seed production,” he said.
The other technique uses an implement that wipes herbicides on the taller weeds and not the crop.
“In this case we’re having maybe a bit more mixed success. This is still research, so we don’t have recommendations to producers yet,” he said.
“One of the key things is we’re not affecting the yield of the crop that much. We’re just targeting weed seed production in this case.”
Shirtliffe said the time has come to stop letting kochia grow each year in saline spots, which he refers to as kochia nurseries. It’s where herbicide resistance starts, and continuing to seed a crop in it is risky behaviour for the entire agriculture industry.
“You’re selecting for it and doing a breeding trial. You’re a kochia breeder, right?” he said.
“I think we have to start looking at ways of managing saline land to pull it out of production. Don’t wish every year there’s a white crust on the surface and think that going through and seeding magically this year is going to get a good crop in there. No, it’s not ever going to be a good crop.”
Producers need to spatially isolate those parts of the field, and suggestions include mowing the kochia down before they go to seed and tumble. One long-term solution is to plant grass.
“It’s not doing any good to manage salinity or to manage it from a weak point of view,” he said.
“It’s just wrong on so many levels and not making people money. That’s the trouble, right?”