By Darren Hefty
It’s hard to pick up a farm publication and not hear about cover crops these days. Brian and I get asked about cover crops almost every day on Ag PhD Radio (Sirius XM 147 at 2 p.m. CT). Here are the most popular questions we’ve recently received, along with our answers.
Will My Residual Herbicide Hurt My Cover Crop?
We almost always suggest planting a blend of crops for cover. This way you hedge your bet in case one or more species are affected by a soil residual herbicide from the previous crop. If you applied a soil residual herbicide 90 days ago, for example, much of that herbicide may already be gone. Herbicides are taken up by plants and broken down. They are also broken down in a number of other ways including by soil microbes, heat, and moisture. Spring-applied residual herbicides damaging cover crops is normally not a big issue, but there certainly are some species used for cover that are sensitive to specific herbicides. The good news is even if your cover crop gets slightly damaged, it can still provide good benefit. It’s not like damaging your cash crop, where any injury can hurt your bottom line.
Should I Fertilize My Cover Crop?
Most people don’t, but then again there are quite a few people who don’t fertilize sunflowers or soybeans either, and that doesn’t always work out the best. If you want your cover crop to grow quickly and get thicker, fertilizer can often help. Soil testing will give you a good idea of what’s needed. If you won’t be harvesting the cover crop, all that fertility should be left in the field – likely in an available form for future crop uptake.
What About Using a Cover Crop in a Field with Weed Problems?
Crop canopy provides very good weed control. Quickly establishing a thick cover crop can definitely hold back weeds. Spraying a herbicide over a blend of cover crops can be difficult, though, especially if you have broadleaf and grass crops mixed together. This is one of those situations where you may consider using just cereal rye (if you have broadleaf weed problems) or just a broadleaf cover crop (where you have grass problems) so you have a herbicide option to use if the weeds get off to a good start.
What are the Biggest Reasons People are Using Cover Crops This Time of Year?
There is a whole lot of growing season left. The more time you leave soil with little to no cover, exposing it to wind and rain, the more soil loss you will experience. Also, there are a large number of farmers interested in keeping something living in their fields as long as possible to support soil microbial life. Add to that farmers who would like an area for livestock to graze or bees to thrive or a wildlife habitat, and you’ve got a whole lot of reasons you may consider using a cover crop on your farm.