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A field experiment was conducted at Scott, SK, from 1999 to 2001 to determine the combination of seeding date (early-May, mid-May, and late-May) and weed management system (shallow-seeded untreated, shallow-seeded with pre-emergence tillage, shallow-seeded herbicide, deep-seeded untreated, deep-seeded with pre-emergence tillage, and deep-seeded herbicide) that would optimize yield of field pea grown without the use of herbicides. The shallow and deep seeded pre-emergence tillage treatments were a 2.5-cm seeding depth followed by two sequential harrow passes and a 7.5-cm seeding depth followed by two sequential rod-weeder passes, respectively.
None of the weed management systems had a significant effect on field pea density. The herbicide treatments were the only treatments that had a significant effect on weed density as the application timing was more synchronous with weed emergence than were the tillage treatments.
The pre-emergence tillage treatments reduced weed biomass when seeding was delayed until mid-May following weed emergence. Deep seeding followed by pre-emergence rod-weeding was more efficacious in reducing weed fresh weight than shallow seeding followed by pre-emergence harrowing; however, they both provided similar yield responses at the mid-May seeding date. Delayed seeding until late May resulted in a 30 to 35% reduction in field pea yield compared with early or mid-May seeding, respectively. Early-seeded field peas followed by an in-crop herbicide application resulted in the highest field pea yields with the best seeding date by pre-emergence tillage combination achieving 81% of these yields.
A strategy for field pea
who choose not to use herbicides would be to delay seeding
until some weeds emerge and seed at a 7.5-cm depth followed by
rod-weeding passes prior to crop emergence.
© 2012, Organic Agriculture Centre of Canada (OACC)