We planted a big mix of winter cover crop seeds on 29 acres on September 14, 2012. This was our fourth consecutive cover crop planting. Faced with delay in full-time farming plans and getting livestock, we’re trying to use the time wisely and improve our burned-out soil so it will make high quality grass for our future livestock. Planting cover crops is essentially “Plan B” farming for us. And yay, it’s working!
How Our Soil Needs to Improve
We’re located in Southern Maryland, close to the Potomac, on very sandy soil. Charles C. Mann’s new book, 1493, has a map of the Eastern seaboard titled “Deforestation of America, 1500”. Our farm is clearly located in the large coastal area that was cleared by the Eastern Indians for farms and villages probably 500 to 600 years ago. This history, combined with centuries of hard tobacco farming, explains why our soil is so poor. So we have a lot of work to do in the soil improvement department! And we’re using plants (cover crops – nothing is removed from the field) to help. Here’s our wish list:
- Double Organic Matter: Soil tests say it is barely 2%. We want 4%. We know this takes time, and we’re using particular plants that have huge root systems to help. All plants ooze sugary compounds out of their roots to attract a beneficial microbe community, and some do this more/better than others. The root exudates are complex forms of organic matter, the roots themselves will eventually decay into organic matter, and microbes help speed up the growth and decay cycle.
- Chocolate Cake! Yummm… but I’m talking about soil structure. We want dark, loose, crumbly soil that smells good. Large pore spaces let air and water percolate through and provide a luxury living space for those essential soil microbes and bugs. When we first got this farm in 2008, the soil was depressingly dusty and crusty. The soil structure has improved significantly – we now see nice aggregates – but we still have a long way to go.
- Big Fat Adult Earthworms: I have sadly never ever seen one of these in our fields. We are thankful to now have earthworms (we didn’t in 2008), but they are small and skinny. Adults with orange collar bands reproduce and are an indicator of good soil. We are planting particular cover crops that entice the big guys.
The Ultimate Winter Cover Crop – Explained
Following on our good experience with our summer cover crop mix (cocktail), we chose a winter mix of some of the best plants that meet our wish list items: Austrian Winter Peas, Oats, Cereal Rye, Sweet Blue Lupines, Crimson Clover, and Tillage Radishes.
Rye and Oats: These cool-season grasses have large root systems where soil microbes and bugs can hide out over the winter. In the spring, rye’s growth will really take off and produce good, lignified (carbon) biomass. The mowed clippings will make great mulch to protect the soil from hot summer temps. The microbes, root masses, and high carbon mulch will all work to boost soil organic matter.
Legumes: This will be our first experience with lupines, Austrian winter peas and crimson clover. We inoculated these three to give them the best chance to produce nitrogen for the soil. On top of the N benefit, this site says lupines have an aggressive taproot that will improve the lower soil profile. Crimson clover has fine roots that help build a mellow soil structure (chocolate cake) and attract soil microbes. I’ve heard that winter peas might be one of the best plants for mellowing soil, and they provide good amounts of tender biomass in the spring.
Brassicas: Tillage radishes are mighty soil-moving machines. They drill down into the soil profile and will even root down past compaction layers, opening up the deep soil to let air and water percolate through. Our very sandy soil doesn’t have big compaction problems, but getting plants that go that far down – typically over 30” – is all good for any soil. Big fat adult earthworms are also strangely attracted to these radishes!
We’ll mow-kill this cover crop in late spring when most of it is flowering. Depending on how our farm plans are working out, we’ll either plant our last cover crop or our final pasture grass mix. I’ll also be posting on our Fall 2012 soil test results. I’d like to see if any cover crop benefits show up on soil tests. Stay tuned!