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Cover crops in Iowa are typically seeded in late summer or fall. The most common cover crops are winter small grains like cereal rye or winter wheat. But farmers are increasingly interested in diversifying the cover crop portfolio in Iowa. In this trial, cooperators wondered: Can frost-seeding small-seeded brassica species into crop residue be an effective spring cover crop strategy? Because mustard and rapeseed have relatively small seeds, some have wondered if frost-seeding these into crop residue in the early spring could be an effective 40- or 50-day cover crop strategy. Read the new report here: Spring-Seeded Brassica Cover Crops.
How was the trial conducted?
Three PFI farmer-cooperators participated in this project: Steve McGrew (Emerson, SW Iowa); Jeremy Gustafson (Boone, central Iowa); Chad Ingels (Randalia, NE Iowa). In the early spring, cooperators hand-seeded brassica cover crops into soybean stubble in small plots measuring 7.5 ft x 25 ft. McGrew screened Trophy rapeseed, Daikon radish and Pacific Gold brown mustard. Gustafson and Ingels evaluated Dwarf Essex rapeseed, Kodiak brown mustard and Purple Top turnip. All cover crops were seeded at a rate of 5 lb/ac at each location.
Before terminating the spring cover crops, cooperators evaluated each species for the amount of groundcover provided.
At McGrew’s, the Pacific Gold mustard provided nearly 25% groundcover which was significantly greater than the Trophy rapeseed (11%). The Daikon radish did not establish. At Gustafson’s and Ingels’s, Kodiak mustard was the top performer. There were no differences between the Dwarf Essex rapeseed or Purple Top turnips, though. The cover crops at McGrew’s and Gustafson’s provided approximately twice as much groundcover as those at Ingels’s.
Not surprisingly, more GDD were accumulated in the southwest (McGrew) and center (Gustafson’s) than in the northeast (Ingels) and this translated into more groundcover by the cover crops at McGrew’s and Gustafson’s.
“I might try this on a larger scale and try to plant [the cover crop] sooner,” McGrew says. “[This technique] might fit where the [fall-seeded] broadleaf cover crops don’t overwinter well. I am considering planting a winter-kill grass like oats or barley and then maybe mustard and rapeseed broadcast during the winter before corn.”