As swath timing and harvest approach, it’s time to pay close attention to pre-harvest intervals.
“PHI or pre-harvest interval is a really important concept to understand, and it’s actually a really easy concept to use,” says Keith Gabert, agronomy specialist with the Canola Council of Canada, in this episode of Canola School.
“The labels are really specific about the number of days between the time you apply a product, and the time that you’re allowed to cut it — swath it, or combine it, doesn’t matter,” he says. What confuses some people is the term pre-harvest interval, in that it’s actually the time of application to the time you have ceased growth in that crop, at that ends at swathing.
PHIs are important for products such as insecticides, that might be applied late in the season, or for harvest aids that are applied as part of a dry-down process or for per-harvest weed control, says Gabert.
Insecticide PHIs range from 28 days, to one day. Harvest aids, generally tend to be less days than an insecticide, but it’s important for growers to understand the number of days they’re required to wait to do another operation in that field. (Story continues below video)
Gabert recommends reading the product label, or checking out the Canola Council’s spray-to-swath calculator, on their website.
PHIs ensure that the residue from a product will have either dissipated or have been reduced to negligible levels, or levels that are considered safe to the consumer, by harvest time.
“While you might consider yourself a canola grower, really you’re a canola meal grower, or canola oil grower, you’re providing food for people all around the world. We want to make sure that that food is safe, healthy, nutritious, and meets any of the covered requirements for the product that you’ve used, on that product while you’re growing it.”
One of the challenges to assessing canola is making sure the crop is uniformly mature and that the crop is far enough along, says Gabert. Thirty per cent seed moisture of the crop is the general recommendation, but product to product, the crop needs to be at that moisture stage, or drier, before the product can be applied.
Seed colour change, and seed moisture can be quite different, but regardless, Gabert says to open the pod up and assess. For swathing, 60 per cent seed colour change is the time to get into the field.
Look for the greenest parts of the field and make sure those areas have reached the targeted moisture, for swathing or applying a harvest aid.