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 come 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 spieces speeds decomposition and offers the bonus of edible mushrooms.