How to Improve Vegetable Garden Soil
Whether your farm has acres under cultivation or a vegetable patch on the back 40 – feet, that is – by tending to your soil’s needs over the cold months you can reap rewards that grow year to year.
Think of it, soil experts say, as putting the garden to bed. While there’s a lot more sweat and planning involved in winter soil care than in, say, one night’s reading of Goodnight Moon, tucking in a child and tucking in a garden are a lot alike.
Good soil care, year after year, is as important as consistent child-rearing. At Howell Living History Farm in Lambertville, New Jersey, the scars of plowing practices that promoted erosion in the 18th century are still visible.
“We’re plowing less than they did on our farm in 1880,” farmer Rob Flory says proudly. That plowing is done with horse or oxen teams. Excess rainfall that once carried soil out of tilled fields is now borne by grassed waterways, slowly across gentle slopes, running clear into a stream and a pond on the property.
It’s just one way the historic 130-acre farm, owned and operated by Mercer County, cares for its most precious resource.
“We’re not going to sacrifice our soil,” Flory says.
Laying out the future
Preparation to put a garden – or farm fields – to bed takes planning. Knowing what crop will be planted helps direct decisions about where it will be planted, and how you’ll want it to look. Think of it as laying out a child’s clothing for the next day.
At the Seed Savers Exchange Heritage Farm in Decorah, Iowa, gardens are always rotated into and out of pasturelands. Shanyn Siegel, collection curator, says new plots are carved from ground where cattle kept weeds in control and contributed manure; older plots are returned to grazing.
“And the gardens that we take from a space that was formerly pasture, those are the Cadillac of gardens,” Siegel says.
At Howell, a traditional eight-year schedule is in place for field crops: hay, then corn, then oats, and then a wheat/timothy/clover combination, on which hay will be cut for five years, allowing that field to be unplowed for that stretch of time.
Crop rotation, whether it’s as simple as avoiding planting tomatoes in the same raised bed year after year, or something on the scale of Howell’s orchestrated grain dance, discourages both disease and some insect pests. So it’s worth taking the time to sketch out a plan for your particular space, noting what worked well and what didn’t in the most recent harvest and any problems in need of solutions. Come spring, it can be too easy to forget what went where and what results were obtained. (GRIT‘s Food Garden Planner now includes a crop-rotation feature that does the thinking for you.) It’s also a good time to hit the books or the county extension phone line to get answers – or a soil test (see “The Report Card: Soil Testing”). If, like Seed Savers, you plan to create a new garden out of pasture, consider removing or tilling in the current vegetation and applying any needed amendments tailored to the patch’s future.
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With your garden’s future laid out, there’s now some cleanup involved – just as you would have a child wash face and hands and brush teeth, maybe even take a bath.
You’ll want to remove any plant material that showed a hint of disease. While it’s possible to compost such debris at high enough temperatures to kill some pathogens, it’s likely not worth the trouble. Some gardeners remove all nightshade plant debris on principle to deter blights and viruses.
Overall, your cleanup strategy will be particular to your area and the crop. For example, on eastern Colorado’s High Plains, farm consultant and state fair vegetable judge Larry Propp recommends leaving old squash vines or other stubble on the fields to help hold snow in place. That’s because the area is subject to whipping winter winds that easily carry off precious moisture.
Soil-amending season is a fine time to prune any damaged tree limbs and uproot anything you don’t want self-seeding next year. If you till in the spring, remove and inventory trellises, cages, temporary fencing and plant markers, and check the condition of infrastructure. One last weeding before the snow flies can pay off well too.
Soil experts agree there is nothing like manure – nothing in the world.
Abundant manure, whether spread with a turn-of-the-century manure spreader or dropped as the cattle graze, is the uniting force of soil fertility. You could call it the Force. The biochemical duct tape that holds great soil together. Top Dung.
“Cow would be No. 1,” Propp says. “And after that, horse.” Sheep is fine, he adds, but can be difficult to obtain. If you have sheep for neighbors, count your blessings and find ways to ingratiate yourself with their shepherds.
“A lot of people spend a lot of money on bagged manure in the spring, but if you can get the stuff locally and spread it in the fall, you’ll be way ahead in the spring,” says Joel Reich, Boulder, Colorado, extension soil scientist.
At Howell, “the manure spreader really does get a workout,” Flory says. Because the farm’s livestock – cows, horses and oxen – are stabled at night in winter and during the day’s worst heat, collected manure is always in abundant supply, not to mention what’s dropped in place.
“The first principle,” Siegel says, “is to return to the soil what you take out of it.” Manure from grazing animals does just that.
In the kitchen garden or vegetable patch, Reich recommends spreading a 1-inch-thick layer of manure. Then he likes to sprinkle blood meal, a nitrogen supplement available at most garden stores, on top.
Into that 1-inch layer also can go kitchen or garden waste, or compost – thoroughly chopped – as long as it’s nothing from the nightshade family. Bags of crushed fall leaves can join the mix, andso can chopped straw, if you’ve got it.
A trip to the comfort station
Remember that child who just wouldn’t stay down for the night? Who kept popping up for one more glass of water – or potty trip?
If you’re in a dry area – or one that’s suffering from a temporary or extended drought – treat your composted or manured plot to a nice long, slow drink. The worms, bugs and bacteria that break down compost’s nutrients into smaller and smaller chemical bits, making it available to plant roots, need moisture to do their work. If you’ve turned off or removed drip irrigation, wet your amendment-covered garden down with a sprinkler.
“Lay it out and wet it down,” Reich says, but “don’t firm it – let the water settle things.”
And if you’re in an area with dry winters, a soaking every month or so can’t hurt. Sometimes, that child just stays thirsty.
Once you’ve laid down that manure layer and given it a drink, tuck it in with a blanket.
It can be any kind of covering you can muster, says Reich – space being the only real limitation. You can use tattered old bedsheets, tarps or row covers; Reich has even used large, flattened cardboard boxes, obtainable at appliance stores, well-wetted and held down with rocks or pavers. (In some soils, the cardboard itself will break down to add organic matter.) He’s also used old sheets of plywood: “Reusing is an even higher purpose than recycling.”
What you’re doing, he explains, is creating a compost pile in the soil. “When it’s freezing, when it’s 20 degrees, that garden patch will heat up because it’s bioactive,” Reich says. “You’ve added food with the leaves or manure, nitrogen with the blood meal, and water. That’s your six-month winter compost.”
With the blanket in place, nitrogen added to a covered bed will be consumed and excreted repeatedly, remaining in the soil, Reich says. “In fact, it’s broken down into more and more plant-available forms.”
At Howell, the kitchen gardens are covered thickly for the winter with straw – grown on the farm itself – that is later raked up and added to the compost pile. “It keeps the earthworms really busy in the winter, so they help turn the soil for us. It makes digging really easy in the spring,” Flory says.
Blankets by the acre
Another version of the blanket for larger gardens or field crops is the cover crop, utilized to protect beds, exclude weeds, prevent erosion or provide nitrogen; different cover crops can achieve different combinations of these purposes.
Typical crops are seeded in late summer or early fall to overwinter, then tilled into the soil two to three weeks before vegetables are seeded. But the choice of the crop itself should be carefully contemplated.
In Propp’s region of Colorado’s eastern plains, where annual rainfall is usually only 14 to 18 inches, cover cropping often isn’t recommended because that crop consumes scant and precious soil moisture, then exposes more soil to dehydration when the crop is tilled.
In less arid regions, cover crops are hailed. Seed Savers’ farmers are still testing ways to schedule cover crops.
“We’re in as early as the soil can be worked, usually mid-March,” Siegel says, and harvesting up to frost and past frost. That makes timing tricky. Small vegetable farmers are in a similar dilemma.
Between the farm’s long isolation tents are often wide, unplanted areas. “We’ve been experimenting with annual rye grass, which can handle the foot traffic, just to not have bare ground,” she says.
In Siegel’s own home garden, her cover crop for areas she just hasn’t had time to plant is a tasty one: dill. “It’s something I can save seed from and reseed easily, and if I don’t want it anymore, it’s easy to pull out.”
The Report Card: Soil Testing
Annual soil tests — plus pre-testing of any new garden beds you’re planning for next year — are a good idea. Contact your county or state extension office, or a university with an agriculture department, to find out where to have one done. You’ll be able to check nitrogen levels for vegetables, usually for a fairly small fee. Other chemical tests may be advisable depending on how the land was most recently used, and these may cost extra. If your future garden is near a livestock area or is a former stock area, be sure to ask about salt levels.
At Howell Living History Farm, Rob Flory says the field-crop acres are tested about every eight years; the vegetable garden, about every three years. Based on such tests, the farm’s crews have added lime or calcium or even borax, the last when a clover crop had done poorly and the staff wanted to know why. Soil tests also can reveal problems with pH, salts, low nitrogen or low organic matter.
A soil test usually involves taking a group of soil-core samples, scattered throughout a plot of soil that will have a particular use — mixed vegetables, for example, cut flowers or alfalfa. The samples are mixed and allowed to dry for a minimal amount of time: enough to remove the moisture, but not enough for the nitrogen to decompose. That’s about a day or two for most samples. You’ll usually fill out a form about the field or garden’s history and current use, and choose from among a variety of tests.
The accuracy of over-the-counter soil test kits is notoriously low; it’s worth it to pay the nominal fee for more scientific tests.
No to Nightshades
The nightshade family of plants (Solanaceae) consists of more than 2,500 species and includes eggplant, tomato, potato, capsiucum peppers, tobaccos and petunias, as well as the highly poisonous belladonna, jimsonweed, henbane and mandrake.
Susan Clotfelter is the granddaughter of Illinois farmers Verne and Edith Shepherd, who grew corn, beans, vegetables, turkeys, sheep and an orchard on 80 fertile acres. She gardens in Colorado and blogs at www.DenverPost.com/diggingin.
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