Tillage, Cover Crops and Soil

Every episode of an old TV series opened with people staring at an object streaking across the sky. One man called it a bird, another a plane, and finally a smart-ass proclaimed, “It’s Superman!” No one said it’s Clark Kent!

I was musing how differently we perceive the same thing. I imagine folk gazing at the uncultivated strip on our land saying it is an eyesore, others a haven for wildlife, and gardeners thinking it is a wasted opportunity to grow food. To my mind it was a chance to sow wildflowers, and I imagined the following summer a mosaic of blue cornflowers and yellow Rudbeckia with bees hovering overhead. So I asked a neighbor to plow the strip before I scattered seeds on the freshly turned dirt. I worked to create a nursery of beauty but an ugly bed of cudweed was born that blanketed the ground so no “virtuous” plant could penetrate. I now realize the compacted soil we turned exposed buried weed seeds to light and oxygen so they could germinate.

In the way that broken dreams can be instructive, I started to think afresh about plowed farm fields, how the neat rows of mounds and furrows from the hedgerow to the horizon appeal to my sympathy for geometry. Perhaps the Ohio farm agent Edward H. Faulkner loved the tidy appearance of fields left brown and vacant from winter to spring, but at some moment in his life the image jarred. Perhaps it was the memory of farms in the Mid-West and in Grapes of Wrath country further south where the topsoil was blown away in the Dustbowl that stirred him as a younger man. Maybe he pondered the benefits of leaving the land idle for which FDR’s New Deal compensated farmers with $2 an acre. I wonder if he cast back in his imagination to the lush native grasses of the original prairies that used to anchor the soil against storms and floods until they were plowed by settlers hungry for land who brought farm practices that had served their ancestors well in past centuries in Europe but were not such a good fit to prairieland.

Faulkner suspected soil erosion wasn’t so much caused by relentless forces of nature like climate hostility and grasshopper plagues as by deep plowing. Perhaps gentler tillage with a new tool or no turning of the soil would protect the land without diminishing the harvest. When he published the Plowman’s Folly in 1943 he was ridiculed, and like a good many other pioneers had to wait for his prescience to be honored.

Topsoil is a thin, fragile crust on the earth. Without soil and the fertility it harbors this would be a barren planet, so its care is a supreme responsibility. But as human populations shift from rural living to cities we seldom, if ever, think about it.

The USDA estimates we lose three tons of topsoil per acre annually, and at that rate we only have enough to support present agricultural practices for another sixty years (Scientific American, Dec 4, 2014). The public and environmental health costs of soil erosion are amounting to $45B every year. Of course, soil is regenerated naturally, but very slowly depending on the landscape and climate and at the oft-quoted average rate of one inch every 500-1,000 years. We can’t wait for nature to correct our errors and must work with her.

There were always reasons (if little scientific evidence) for deep plowing, but gradually no-till practices have caught on and swept into the organic farming movement. What Faulkner didn’t know is that soil has a much deeper structure than is visible in its “horizon.” Every handful contains immense tangles of almost microscopic fungal hyphae that build pipelines around and even inside crop roots for a relationship that benefit both (The Progressive Farmer Feb 2017). By disrupting and burying the network, plowing delays its regeneration.

Sowing a cover crop to clothe the land between harvest-time and spring also helps to reduce erosion, but offers other important benefits. Annual clover and rye grass sown among stubble residues provide soil anchorage, extra nitrogen from root nodules, conservation of moisture, and even affects the microclimate. In the south of France researchers found that by increasing infra-red radiation cover crops keep local temperatures cooler by up to 2° C. on hot days, despite the countervailing effect of reduced evaporation (PNAS 2014).

All-in-all, the farm revolution is helping to reduce soil loss, chemical fertilizers, weeds, and tractor pollution. This started me thinking about my garden, for aren’t gardeners little farmers mimicking agriculture, and isn’t the garden fork a substitute for a plow? My experiment with plowing had been a failure, but it jolted me into letting land be. What’s sauce for the goose is sauce for the gander, and I didn’t need more convincing to retire from digging.

The experiment is still underway. Last fall the raised beds were given a shower of compost over crop residues, and without breaking soil structure I poked drainage holes with a rebar before sowing a cover crop. In previous years after leaving the soil naked all winter it quickly hosted a bed of weeds, but this year the clover and rye grew so thickly they blocked weedlings completely. I mean completely! By February I was ready to kill them off under a black tarp and dig the green manure lightly into the soil after it turned yellow before planting vegetables. The proof will be weighed in June and July, and in pounds of tomatoes and beans instead of tons of corn and soybean. An experiment is like a day at the races, because you can’t count on winning. Gardeners are hardy types like farmers because they live hopefully and consign the history of bad harvests and outdoor labor to some dark cave of the mind.

Next Post: Is the Dismal Swamp still Great?