Soil Care Basics: Protecting Soil Structure
with Alternatives to Tillage
In “Effects of Excessive Tillage”, we considered ways in which excessive tillage is seriously detrimental to soil life and a contributor to greenhouse gases. Proper soil care reduces the need for tillage. Nurture of soil life by constant introduction of organic matter helps to open and loosen soil structure. That improved structure can be protected by practices designed to do one thing: keep the soil covered at all times. Repeat after me: “No bare soil!”
An obvious way to keep the soil covered is the extensive use of organic mulches. It is often said that high-carbon materials such as straw or leaves are not good additions to soil, since soil microbes “rob” available nitrogen from the soil in order to break down the excess amounts of carbon. This is true, however, only if we incorporate these high-carbon sources into the soil. I once tilled in some coarse compost containing large amounts of oak leaves not yet fully decomposed, and found that crops grew quite poorly there the entire season. However, if high-carbon materials are laid down on top of soil as mulches, there is no problem. The mulch benefits soil life by retaining soil moisture and protecting against temperature extremes (freezing chill in winter, blazing heat in summer); and microbes, earthworms, etc. can “nibble” at the mulch in the contact zone between soil and mulch, a layer of intense biological activity, and slowly incorporate their residues into the topsoil. Actually, high-carbon mulches are preferable to materials that decompose readily, since they persist longer before being incorporated into the soil food web. (Every gardener who has used mulches knows the story: You put down a nice thick layer early in the season, then suddenly one day notice—The garden ate my mulch!) Even so, it is usually necessary to renew mulches that are in place for the entire growing season.
It is often recommended to turn manures and composts into the soil, but if we wish to reduce tillage and attendant soil life disruption, it is possible to apply the manure or compost on the soil surface, and keep it from drying out (hence degrading) with a thick high-carbon mulch (along the lines of “sheet mulching,” described above).
Grass clippings should not be lost as a resource—certainly, shipping them off to the landfill is a crime against sustainability. Unfortunately, grass clippings from a power mower are difficult to use efficiently for either composts or mulches: They mat down and become putrid (rot) in a slimy layer which inhibits transfer of oxygen into a compost heap or into the soil. A grass-clippings mulch can be hazardously slippery underfoot, and most unpleasant to work on. I much prefer to let lawn or pasture grasses grow to eight to twelve inches, then cut with a scythe, rake after a couple of days drying out a bit, and apply where needed. The scythe may be the homesteader’s best friend.
An undervalued potential source of organic matter is the huge volume of wood fiber the typical family “exports” in the form of newspapers and cardboard. I never send these into the waste stream anymore, but use all that comes my way for mulching. All the reading I’ve done on the subject convinces me that modern newsprint in this country, and cardboard produced in the United States and Europe, do not pose environmental hazards. When establishing “kill mulches” (mulches over a living grass sod intended to kill it in preparation for planting trees and shrubs), I lay down a thick layer of newspaper/cardboard, then cover with leaves, grass cuttings, etc.
Wood chips make good mulch for some situations—e.g., pathways, kill mulches where trees will be planted, etc.—and are often free for the dumping from tree-trimming services. Inoculating chips with spawn of wood-loving mushroom species speeds decomposition and offers the bonus of edible mushrooms.
A key strategy for protecting soil structure is to grow in wide beds and restrict foot traffic to the pathways—thus avoiding compaction in the growing areas—and to plant as closely as possible in the beds. Close planting boosts bio-activity in the soil, since as noted earlier, the zone of greatest activity is the rhizosphere in and immediately surrounding plant roots. It also shades the soil surface, benefiting both soil life and plants by conserving soil moisture and moderating temperature extremes.
Interplanting slower-growing with faster-growing crops can help keep the bed constantly covered. For example, rows of carrots in the bed can be interplanted with radishes and/or beets, both of which mature earlier than the carrots. As we harvest the radishes and beets, the carrot tops meet and interlace, closely shading the bed. Similarly, brassicas such as cabbages and broccoli can be interplanted with faster-growing lettuces. The strategy of undersowing cover crops, noted above, also helps keep the bed covered when planted to an appropriate food crop. Such strategies also reduce weed pressure, further obviating the need to till the soil.
Paths between beds
Don’t forget soil-care opportunities offered by paths between beds. Mulching the paths also protects garden soil from drying and from temperature extremes. In addition, foot traffic helps shred or grind mulch materials such as straw or leaves. From time to time, this finely-shredded material can be transferred to the beds, where it will break down much more readily than in its coarser forms.
Another possibility is to allow somewhat wider pathways, plant them to cover crops that can take a fair amount of foot traffic (rye, Dutch white clover), then cut the path covers from time to time with a sickle and use them for mulches in the beds.
Other Minimal-Tillage Strategies
Consider well before assuming that tillage, especially power tillage, is “necessary.” Almost invariably, alternatives exist. Power tillers are stressful to use—loud, stinky, and jarring—and worse, invert and mix the different layers in the soil profile, disrupting the soil food web and breaking down the “crumb” structure we and our friends in the soil have worked so hard to achieve. Even garden-size tillers tend to form “plow pans”—compression zones formed by “spanking” of the soil by the rotating tines—which resist penetration by water, earthworms, and plant roots. Even in the case of cover crops which must give way to the planting of a harvest crop, it is not necessary to turn them into the soil, as usually recommended. When working at the garden scale, alternatives include: Simply bury the cover crop under a sufficiently heavy mulch to kill it. (You’ll be amazed at how quickly the soil life digests it.) If the soil is in loose, friable condition, it is easy to pull the cover plants up by the roots and lay them on the bed as mulch. Certain plants such as rye and vetch are difficult to kill without tillage, but cutting them immediately above the crowns after seed stalks or flowers form will kill them. Use the sheared top growth as a mulch to help break down the roots more rapidly. Chickens can be used to till in cover crops. They cause some disruption of soil life, of course, especially fungal hyphae networks and the larger animals such as arthropods, nematodes, earthworms, ground beetles, etc. However, the disruption is only in the top couple of inches of soil, does not invert layers or pulverize structure deeper down, and is likely to be quickly repaired, especially as the birds’ droppings give a boost to bacteria and other soil life.
When it is necessary to loosen the soil at depth—as in a “young” garden whose soil has not yet “mellowed” sufficiently to grow good root crops—I recommend the broadfork, a hand tool that, like the scythe, makes joyful, all-round use of the body in a rhythm that becomes a garden meditation. Unlike a power tiller, the broadfork loosens the soil without inverting its natural layers or breaking down its “crumb” structure which we and our soil allies have worked so hard to achieve.
The broadfork is much easier to use in soil that is already in fairly good condition—it is not the tool of choice for converting a tough grass sod over compacted soil to new garden ground. Does that mean that in this case we are forced to revert to power-driven steel? Not on my homestead, where once again chicken power comes to the rescue. Normally I would rotate the birds on to another plot after a week or so to prevent excessive wearing of the pasture sod, but in this case “excessive wearing” is exactly what I want. I use electronet to “park” a flock of chickens on the sod I want to convert to garden. With their constant scratching, the birds kill and till in the sod. I remove the birds, grow a mixed cover crop, and then return the chickens for another round of tilling. Now the new ground is ready to start working as garden. Be sure to note the state of the soil before you start—the changes by the end of the season will amaze you.
If you don’t have chickens, a no-till way to develop new ground is to lay down a “layer compost” or “sheet mulch,” (described in Increasing Organic Matter: Composts), heavy enough to kill the existing sod. If you can be generous with watering through the germination phase, you can start a cover crop in the top layer of the sheet mulch, the roots of which will greatly accelerate the breakdown of the mulch. Plant a second cover in the fall. This strategy works better if you can give the area over completely to soil building for a full year. If you have to get some production out of the ground the first season, simply open up holes in the sheet mulch and plant (a strategy that works better with some crop plants than others).
One way to get significant production on new ground in the first season is to use potatoes to do the heavy work for you. Simply lay your seed potatoes directly on the established sod, and cover with a thick mulch. As the sod plants die, their fresh green matter converts readily to a flush of available nutrients for the heavy-feeding potatoes, and the potato roots speed breakdown and loosen in the root zone of the sod. Renew the mulch as needed to keep the growing tubers well covered. When time to harvest, simply push the mulch aside and pick up your spuds. The new garden soil still has a long way to go, but it’s well on its way.
The only time I do disruptive tillage in the garden is when digging root crops such as potatoes (if not mulch-planted), sweet potatoes, and burdock. With such crops, I dig deep and thoroughly with the spading fork—a total disruption of soil structure and inversion/mixing of its natural layers. My goal, however, is to make such intensive disruptions the rare exception rather than the rule, and trust that the intact soil life communities in surrounding beds will soon help reconstitute the soil food web in the disturbed areas.