When I started working with the Land Stewardship Project on the Chippewa 10% Project, the work felt far away. Based out of Minneapolis, I was working on the Cropping Systems Calculator to help farmers in the Chippewa River watershed region in west-central Minnesota determine what financial differences they would see by switching a marginal corn/soybean field to a more conservation-minded practice, or to keeping a field covered past the typical 110-day row crop growing season.
Two weeks after starting, I joined LSP organizer Robin Moore for a day of farm visits and soil sample collecting in the Chippewa River watershed region with members of the Cover Crop and Soil Health Network. Each farm and its cover crop use was unique. After planting a cover crop during a dry August, some farmers had low germination rates while others had a field of volunteer seeds from a previous crop. Many used mixes of as many as seven species, and no two farmers used the same exact seed blend.
But each farm did seem to share one common characteristic: the use of tillage radish as a cover crop. We pulled one up at almost every farm to see how far down the tuber went and imagined how much further the taproot went into the soil. Everyone seemed excited about the chance that these mighty brassicas were breaking up the compaction caused by years of running tractors and large implements over their fields.
This layer of compaction, also called the hardpan, is a major concern. Large scale agriculture and the use of heavy equipment may have increased productivity, but farmers are now seeing the consequences of years of plowing or even just driving large machinery like tractors or combines across fields. These repeated actions have created a dense layer of soil which is all but impenetrable to both water and plant roots. Traditionally, a tractor attachment called a subsoiler is used to rip through the hard layer of compaction to allow plant roots to access deeper soil, but many farmers are now questioning if this is the best method.
After pondering this question, many are experimenting with a method called “bio-drilling,” using plants to break up the hardpan. As the most recent Land Stewardship Letter reports, veteran no-till farmers in Indiana are utilizing bio-drilling to do the work of mechanical rippers, saving money and time in the process.
Various crops are capable of bio-drilling, but tillage radishes are the most popular and may be the most practical. Growing and decomposing rapidly, the tillage radish can grow two feet long with a taproot as long as six feet. It breaks down quickly and provides root channels for spring crops, making it easy for their roots to go beneath that packed layer of soil.
Many who are using it are beginning to see unexpected benefits from the popular cover crop. In addition to breaking up this layer of compaction, tillage radishes provide organic matter to improve soil health, allow water to infiltrate deeper into fields instead of running off, and allow roots to access the nutrients being stored below the topsoil. These additional benefits help plants in times of extreme weather—both overly wet or dry periods—which are becoming more and more common.
The benefits of using tillage radish as a bio-driller aren’t going unnoticed by those outside the farming community. The landscapers of the Gateway Arch in St. Louis recently faced a similar dilemma to many farmers, although their compaction issues were caused by millions of yearly visitors walking on the grounds. In an attempt to avoid using heavy machines, they decided to try the trendy tillage radish during the fall of 2015.
Drawing the curiosity of many visitors, the landscapers say that the experiment has been very successful. Knowing that just bringing in new topsoil wouldn’t ensure the health of 900 newly planted trees, the landscapers used tillage radishes to create deep pathways for the tree’s roots to grow into, producing stronger, healthier trees. Hoping to plant tillage radishes again this fall, the landscapers are confident that the cover crop will work better than a subsoiler when it comes to helping the trees establish themselves. It turns out they do more than just break up compacted soil.
“That’s the beauty of these radishes,” said arborist James Sotillo in a St. Louis Post-Dispatch article. “As they grow, they’re releasing all of these incredible metabolites into the soils.” Managers of other highly-trafficked green spaces are taking note and officials at Central Park in New York City are pursuing tillage radishes as a method of breaking up compacted soil in the near future.
As I have continued to work with LSP, my understanding of the utilization of more complex mixes of cover crops has evolved, but my life in the city and work in rural areas seemed separate—that was until hearing about the Gateway Arch in St. Louis. Now, in addition to being able to identify various farming practices in crop fields, I view the green spaces of Minneapolis differently. I wonder if I’ll be seeing tillage radishes at Minnehaha Falls, the Minneapolis Sculpture Gardens, or my neighborhood softball field. Farmers like those in the Chippewa 10% Cover Crop and Soil Health Network are experimenting with various cover crop mixes and their benefits—now I’m waiting for the Twin Cities to take note and copy their innovative ideas.
Many times it’s believed that innovations disseminate solely from urban hubs outward. LSP may have a Minneapolis office, but our strength comes from our rural base and the creative ways farmers balance environmental sustainability and profitability. The use of tillage radish, bio-drilling and similar soil health practices is one example that innovation is a two-way street.
Rebecca Wasserman-Olin works in LSP’s Twin Cities office, where she is developing economic decision-making tools for farmers in the Chippewa River watershed. Look for the tool to be published on LSP’s website later this spring.