Taller cultivars, doubled seeding rates and a crop rotation that includes peas pays off handsomely in wild oat suppression and reduced input costs.
Led by weed scientist Neil Harker of Agriculture Canada’s research centre in Lacombe, Alta., federal researchers at Lacombe, Brandon and Beaverlodge, Alta., have found that Test 42, a rotation of direct seeded barley, canola, barley and peas, resulted in a 70-fold decrease in wild oats compared to five continuous years of short barley grown under identical conditions.
“Our main focus is to increase crop health. If you can do that, then you are going to reduce the need for herbicides,” Harker said.
Read Also
Going beyond “Resistant” on crop seed labels
Variety resistance is getting more specific on crop disease pathogens, but that information must be conveyed in a way that actually helps producers make rotation decisions.
“Basically, we had healthier plants to compete with weeds.”
Researchers applied standard herbicides such as Assert, Puma and Achieve at a one-quarter rate in both plot types.
Tall cultivars AC Bacon and AC Lacombe were compared to shorter varieties Peregrine and Vivar.
Seeding rates in the four by 15 metre plots were doubled, from 200 seeds per sq. metre to 400 per sq. metre. Fertilizer application was applied based on soil testing.
Two better than one
Doubling the seeding rate cut wild oat biomass by 300 percent, and the taller cultivars had half as many wild oat plants. Combining both strategies resulted in eight times fewer wild oats.
But the biggest surprise came when researchers looked at the results of the full combination of crop rotation, tall barley and double seeding rates: wild oat biomass plunged from 1,800 kilograms per acre to 25 kg per acre.
Little difference was found between the two in Year 3 when barley was growing in both test areas, but disease and weeds were inflicting heavy losses by the fifth year, when short barley had been grown for five years straight.
“By Year 5, diseases had started to build up in the continuous barley and there were quite dramatic differences,” said Harker, adding that the better managed plots were yielding on average 30 percent more.
(See Proper practices, page 2)
Harker said six years of the study have been completed and a full economic analysis will be presented once the eight-year study is finished.
“In terms of economics, it’s pretty easy to make a rotation look good when you don’t have to apply nitrogen for peas. Also, increasing the seeding rate of barley is pretty cheap.”
Diverse rotations pay off in healthier soil and crops by giving soil microbes a more varied diet of root matter to feed on, especially when a legume such as peas is thrown into the mix.
Shade is the biggest factor in weed management, he added.
“When you think about it, a barley canopy that is nice and green versus one that is diseased, which one is going to shade out the weeds better?”
Of course, using full rates of herbicides would have wiped out the wild oats, but Harker said the point of the study was to show that a system for promoting crop health could reduce dependency on herbicides, which is becoming more important given the risk of resistant weeds.
