Guide to Soil Improvement for the Garden

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Without question, the key to our growers' soil fertility successes is that gardeners' god-send . . . compost.
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While your garden plot becomes buried by snow, it’s time to learn how to improve your land by using this guide to soil improvement for the garden. (See the garden composting photos in the image gallery.)

“A healthy garden is teeming with life forms, which all interact to make its ecosystem function smoothly. We, as gardeners, must learn to live and work within that system without disrupting it, taking from it what we need but always giving back more than we take.”
Barbara Sullivan

“Scratch your garden’s back, and it’ll scratch yours.”
Kerry Sullivan

Three issues ago, in a piece entitled “A Visit With MOTHER’s Gardeners” (see MOTHER EARTH NEWS NO. 75, page 62), we introduced you to the lushly productive garden beds at our Ecological Research Center and to the two growers–Kerry and Barbara Sullivan–who’ve made them so fruitful. That article described how the Sullivans’ ongoing soil improvement projects have both given them lavish yields and practically solved their insect pest problem . . . it gave some background on our two master growers along with some insights into their personal gardening philosophies . . . and it shared information about one of the Sullivans’ soil-boosting strategies, the use of “catalyzing” biodynamic field and compost sprays.

However, the piece failed to give any detailed information on the couple’s four other earth-building practices: sowing ground covers, rotating crops, double-digging, and composting. So, since we all recognize that the health of the soil is undoubtedly the single most important factor influencing the vigor and productivity of crops, we wanted to take the time now–while you’re not too busy working in your garden to think about how to improve it–to fill in the gaps left by that previous article with this guide to soil
improvement for the garden . . . and share more of the Sullivans’ wisdom with you.


Every fall, Kerry and Barbara sow rye grain–or a combination (which is predominantly rye) of the grain and hairy vetch–over any garden bed that they don’t intend to plant in vegetables early the following spring. Both winter-hardy ground covers–which should be available at local seed and feed supply stores–serve to help loosen up the soil and control erosion. In addition, each of the two plants has its own unique advantages.

The rye grain, also called winter rye (don’t confuse it with rye grass), is an amazingly quick grower that–while it may get off to a slow start in the chilly weather of fall–bursts into green in the early days of spring. And, in doing so, it provides a great deal of bulk organic matter for the compost pile.

Hairy vetch (also called winter vetch), on the other hand, doesn’t grow as rapidly as does rye . . . however, it’s a hardy nitrogen-fixing plant which actually adds a good bit of that vital–but quickly used up–nutrient to the soil. Our gardeners thus use the vetch primarily on beds that will later grow such nitrogen lovers as spinach.

Before sowing their cover crops, Kerry and Barbara prepare the beds by loosening the soil with a garden fork. They do this by simply swinging the tool laterally into surface clods . . a technique called tilthing (developed by Alan Chadwick, founder of the biodynamic/French intensive gardening method). They then fork up, and shatter, any dirt balls existing in the top 8 to 12 inches of soil. The gardeners work compost into the growing area and treat any hairy vetch seeds with a special inoculant to increase the legume’s nitrogen-fixing ability. Finally, they sow the seed by hand and lightly rake over the soil surface.

When it comes time to harvest their cover crops, the gardeners sharpen flat-edged spades and skim the greenery, by chopping it off–just near the soil line–right under the plants’ crowns. They then pitchfork the cuttings into a wheelbarrow and use them to make compost.

Now you may wonder why the two growers don’t just turn the crop under and there-by save themselves the trouble of harvesting and processing the material. Well, the Sullivans’ response to that query is that green matter takes four to six weeks to decompose in the ground, and actually ties up some of the soil’s nitrogen while it’s degenerating. So it would be necessary to wait more than a month after turning under a cover crop before getting any use out of the nitrogen it could offer! However, since the gardeners skim off their “green manure”, they can plant vegetables in the same growing spaces right away.

When Barbara and Kerry have a cover-cropped bed that’s going to remain unused for a long period in the spring, they just trim back the greenery with a sickle every time it starts to head, and use those clippings for compost. That practice prevents the plants from getting hard and dry–as they do when seed heads form–and can give the gardeners two, or even three, harvests of good compost fodder from a single plot.

Our master growers also often employ a summer cover crop, buckwheat. This warm-weather plant (which, by the way, provides excellent honeybee forage) grows so rapidly and lushly that the Sullivans try to sow it whenever a bed will lie idle for as long as a month or during hot weather. Once again, they use the foliage for compost material. However, Barbara and Kerry point out that many home gardeners could achieve pretty much the same result by simply letting their weeds grow for a month and skimming those plants off before they go to seed. In fact, such indigenous ground covers might reach down and loosen soil more deeply than buckwheat would, anyway.


The Sullivans rotate crops primarily to help balance such nutrients as nitrogen, potassium, and potash in the ground. As Barbara puts it, “The ideal planting sequence would be to start off with a nitrogen-fixing legume . . . follow that with a nitrogen-loving leaf crop . . . then raise a root vegetable . . and finally, after dressing the bed really heavily with compost, grow a heavy-feeding fruiting crop.” However, they’re rarely able to achieve that optimal sequence themselves. Instead, Barb and Kerry often simply divide their plantings into four groups–the root, leaf, legume, and fruiting crops– and avoid planting two of the same type consecutively in the same place.

Furthermore, since crop rotation can also help prevent the spread of soil-carried diseases, our gardeners make an effort not to raise different vegetables from the same family successively in a growing space. They focus this concern mainly on three groups: the cucurbits (squash, cucumbers, and melons) . . . the brassicas (broccoli, cauliflower, cabbage, brussels sprouts, turnips, mustards, collards, and kale) . . . and the nightshades (potatoes, peppers, tomatoes, and eggplant). The Sullivans also tend to avoid back-to-back plantings of members of the Umbelliferae (carrots, parsley, parsnips, and dill) and the Chenopodiaceae–or goosefoot–family (beets, spinach, chard, and lamb’s-quarters).


So much has been written–in past issues of MOTHER–about double-digging that it’d likely be a waste of space for us to cover the procedure in detail here. (EDITOR’S NOTE: For thorough discussions of this topic, ‘see “Biodynamic/French Intensive Gardening” in MOTHER NO. 61, page 92 . . . The Plowboy Interview with John Jeavons in MOTHER NO. 62, page 16 . . . and “Getting Ready for Next Year’s Garden” on page 114 of THE MOTHER EARTH NEWS ® Guide to (almost!) Foolproof Gardening.) Nonetheless, this biodynamic/French intensive technique–which involves removing the top 12 inches from a four-foot-wide strip of soil, loosening the subsoil yet another foot deep with a garden fork, and then replacing the broken-up layer–has been an integral part of our gardeners’ success.

Kerry and Barbara are quick to note that double-digging doesn’t preclude the use of other gardening techniques, though. (“I’m not against rototillers or anything like that,” Mr. Sullivan states.) Yet its distinctive virtues–allowing a person to grow large crops in a small space and to garden completely (and quietly) with hand tools–appeal to a lot of folks. Kerry adds, “There are certain people, like me, who probably wouldn’t have any luck gardening if’ they didn’t double-dig.”

The Sullivans maintain over 100 double-dug raised growing beds in the Eco-Village garden. Approximately 30 of these 4 foot by 30 foot areas are used for perennial crops, including asparagus, cane fruits, and long-lived flowers. The rest are redug on an annual basis, either in the fall or early spring. As Barbara puts it, “You’ll have to decide how often you want to doubledig your beds, but if you really want to improve most soils–especially clay-laden ones–quickly, you’ll redig every year. Fortunately, though, it takes only a couple of hours to work up a well-loosened bed, as compared with the six to eight hours required to dig a 4 foot by 30 foot plot from scratch.”

Of course, the Sullivans can’t redig their perennial beds (doing so would disturb the plants). So, to make up for that lack of regular soil loosening, they incorporate compost–a great deal of it–and some bone meal (as a phosphorus supplement) when they first prepare such areas.


Without question, the key to our growers’ soil fertility successes is that gardeners’ god-send . . . compost. Kerry and Barbara (who make almost 15 tons of homemade humus a year!) work an inch of the soil enricher into the top half-foot of a bed every time they plant a new crop. They use this substance to supply nutrients . . . add the organisms that make for a healthy, living growing medium . . . and create a loose and friable–yet water-retaining–soil. So whether or not you ever intend to cover-crop, rotate plantings, or double-dig, you’d be wise to imitate our growers’ use of this remarkable “soil superizer”. To help you do so, here–for the first time anywhere–is the Sullivans’ formula for brewing batches of brown gold.

[1] Fork up the soil where you intend to build your compost pile. This will allow good drainage from the heap . . . promote air circulation (remember that you’re after aerobic, not anaerobic, decomposition) . . . and make it easier for indigenous worms and bacteria to move up into the pile.

[2] Put down a layer of the coarsest plant material you have. Cornstalks, old cabbage plants, sunflower stems, straw, large plant stalks, or other similar materials will work fine. This rough layer is set on the bottom to help air circulate into the pile from beneath.

[3] Sprinkle on a light splashing of biodynamic compost starter solution. This substance–which helps introduce friendly bacteria into the pile–is not essential for composting success . . . but Barbara and Kerry have found that it increases the rate of decomposition so effectively that they now need turn their piles only once instead of twice, and the quality of the finished product is noticeably improved, as well. (A one-ounce bag of the starter, enough to treat one ton of compost, can be ordered for $5.50 postpaid from the Pfeiffer Foundation, Threefold Farm, Spring Valley, New York.) After mixing up the solution according to the packet’s directions, simply sprinkle the liquid on with a big brush.

[4] Add a layer of manure-filled straw gathered from some livestock animal’s bedding. The excrement contained in this material will contribute much of the nitrogen the pile’s bacteria will need to make humus, while the straw will add some carbon. To assure adequate airflow in the heap, fluff up the bedding with a fork–and break up any large animal “pies”–before adding it. And try to keep the edges of all your layers neat and straight as you work, so you’ll be able to make a large pile.

[5] Sprinkle on another smattering of compost starter.

[6] Add a layer of fresh garden gleanings. Weeds and crop thinnings, as well as pathway and cover-crop skimmings, are all perfect for this application. Such high-cellulose material will add most of the necessary carbon (a good compost pile has an approximate 30-to-1 carbon-to-nitrogen ratio). If some of the weeds still have bits of soil attached to their roots, that’s all the better . . . because the dirt will add its own beneficial bacteria to the heap.

[7, 8, 9, and 10] Repeat the previous four steps–sprinkling starter, adding the manure-straw mix, sprinkling more starter, and adding a carbon layer–until you run out of material. Obviously, you’ll be able to produce a bigger pile if you’ve gathered most of your building materials in advance. (Keep them stored under black plastic until you use them.) And while you’re working, remember to fluff up the layers and keep them thin-around three inches to five inches deep each-to promote intermixing. If the matter seems somewhat dry, water the layers a bit with a hose. (You’re after a pile that has the consistency of a wrung-out sponge . . . but you don’t want it to be too damp.)

[11] Cover the entire pile with black plastic. This will help the mound retain moisture and warmth while keeping rain from leaching out any nutrients.

[12] Wait. Your pile should now start to heat up. In fact, it should get so hot (160 degrees Fahrenheit or higher) within a week or so that it would be impossible to hold your hand in the center of it. After two weeks or a month–the Sullivans recommend waiting a month to give the heap time to complete its early decomposition stages–the temperature will come down to about 115 degrees Fahrenheit (i.e., still hot to the touch, but not unbearably so). At that point you can remove the plastic.

[13] Turn the pile. To do this in the smallest amount of space (and with the least amount of hassle possible), simply turn one three-foot-wide section over onto the soil, next to one of the mounds . . . flip the next “slice” over into the gap created by the first turning . . . and so on until you’ve completely inverted the heap. Then cover the pile again and let it sit another month.

[14] Use it. Your compost should now consist of friable, lightweight, dark humus. It should have absolutely no offensive smell. What’s more, you shouldn’t be able to even recognize its original ingredients. (Indeed, when Barbara and Kerry show a handful of their fresh compost to Eco-Village visitors, many of the people can’t believe the pleasant loam was made from dead plants and animal waste!)


Now that’s precisely how MOTHER’s master gardeners make the lush brown gold that, itself, produces their abundant crops. You can amend their system somewhat, if need be, to fit your personal situation . . . and still make an excellent soil additive. For instance, if livestock manure isn’t readily available where you live, sprinkle a handful of blood meal over each of your organic layers to supply the pile’s needed nitrogen. Likewise, you can incorporate freshly cut lawn grass, fallen leaves (chop them up with a lawn mower first), and household–non-meat–kitchen scraps into the heap. If you don’t have enough material to make as big a pile as the Sullivans construct (their heaps are frequently 4 feet by 6 feet by 12 feet), add ingredients as you can to a three-foot-square area. Once that section gets to be three feet tall, treat it like a little compost pile . . .and start building a new mini-mound right next to it. And you can sprinkle some soil on each layer–to introduce beneficial bacteria–if you don’t want to use the biodynamic compost starter.

Although composting is a relatively simple science, there are a few things that can go wrong with it. If your pile doesn’t heat up properly, first check to see if it’s too dry or too damp. If the former is true, water it a bit and cover it back up. If it’s too moist, mix in an extra helping or two of dry ingredients. If your would–be compost still doesn’t heat up after you’ve adjusted the moisture level, it probably needs more nitrogen. Turn the mound, working in another layer of manured bedding–or a handful of blood meal–as you do so. (On the other hand, if the pile starts giving off an ammonia-like odor, you’ve given it too much nitrogen and should add some leaves, hay, or dried grass clippings.)

Whether you follow the Sullivans’ technique closely or change it to fit your own situation, the crumbly material that you’ll produce will be the finest soil conditioner imaginable. If you feed your garden with that rich humus–and follow other good soil–building practices–next year’s growing ground will reward you with abundance.


We reported, on page 184 of MOTHER EARTH NEWS NO. 75, the beginning of our experiment to evaluate the newly touted soil conditioning technique known as solarization. This process consists of simply covering soaked ground with clear plastic sheeting and waiting a month or so for the sun to heat the earth and “pasteurize” it of most weed seeds and soil pathogens.

Well, folks, the outcome of that test (we have to admit) was . . . poor. Barbara and Kerry put one small winter-rye-to-be fol lowed-by-popcorn plot “under wraps” right next to another similar space last March. They left the covering on for six weeks. The Sullivans say the ground under the tarp never got especially hot (the temperature peaked at around 100 degrees on one 80 degree day) . . . but they also admit this past spring was a particularly cool one.

Surprisingly, what did happen was that more weeds under the plastic patch actual ly germinated earlier than those in the control area. In that way, then, the solar section performed well . . . because when it came time to remove the sheet and plant the popcorn seed, Kelly and Barbara were able to kill–by tilling under-more of the problem weeds in the plasticized patch than in the control one.

However–and this was the most puzzling result the popcorn seed germinated very poorly itself. The Sullivans had about a 40% sprouting rate in the solarized soil . . . where as a perfectly respectable 80% grew in the control plot. (Barb and Kerry resowed the poorly germinated area a couple of weeks later, and that second planting shot up just fine.) Neither of the gardeners could explain that puzzling occurrence.

It should be admitted, though, that our master growers–being devotees of such liv ing soil aids as compost and bacterial sprays–were naturally unexcited about the solarization technique from Day One. After all, they were concerned that the heat might kill many beneficial bacteria as well as pathogens. And, of course, since the number of variables in any gardening experiment is enormous, we in no way consider the data gathered from our limited research as proving anything.

Still, our results weren’t exactly encouraging, were they?