Published Oct 17, 2017

RESEARCH REPORT: Spring-Seeded Brassica Cover Crops
By Stefan Gailans

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.

Kodiak brown mustard at Jeremy Gustafson's on Apr. 24, 2017. Seeded on to soybean stubble on March 2.
Kodiak brown mustard at Jeremy Gustafson’s on Apr. 24, 2017. Seeded in to soybean stubble on March 2.

 

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.

spring-seeded dates 2017
Dwarf Essex rapeseed "frost-seeded" at Jeremy Gustafson's near Boone on March 2, 2017.
Dwarf Essex rapeseed “frost-seeded” at Jeremy Gustafson’s near Boone on March 2, 2017.

Findings

Before terminating the spring cover crops, cooperators evaluated each species for the amount of groundcover provided.

Average groundcover of spring-seeded cover crops at each site in 2017. By farm, error bars above and below columns represent the least significant difference (LSD) at the P<0.10 level. By farm, if error bars overlap, cover crops are not significantly different.
Average groundcover of spring-seeded cover crops at each site in 2017. By farm, error bars above and below columns represent the least significant difference (LSD) at the P<0.10 level. By farm, if error bars overlap, the species are not significantly different.

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.”

For more details on this trial, read the full report: Spring-Seeded Brassica Cover Crops. This project was supported in part by the Walton Family Foundation.

For more information about this study and other studies as part of PFI’s Cooperators’ Program, contact Stefan Gailans at stefan@practicalfarmers.org