|A heavy hay mulch, as promoted by Ruth Stout, smothers weeds (until some, such as quackgrass, creep in) but is not suitable for closely set plants or for grain crops. English photo|
By Will Bonsall
No-till is the rage now and for some good reasons. Plowing, spading and rototilling disrupt the natural soil structure and dilute richer topsoil with low-organic subsoil. Granted, tillage does bring up deep-lying minerals that may have been depleted in the upper layers, but at the expense of using fossil-fueled machinery or onerous muscle power. Deep-delving crop rotations can yield similar results, pumping up minerals from below the reach of most crop plants and sequestering them in organic forms that crop plants can appropriate more easily and over a longer time.
In addition to inverting soil layers, rototilling in particular destroys the crumb structure of soil by repeatedly shattering physical and chemical bonds between soil particles, thus disrupting the natural capillary action by which water moves toward the surface from deeper down. On the other hand, green manure plants restore that crumb structure by binding the whole soil with fine root hairs, which eventually die and decay to form a protective web of humus. This is the main difference between soil and dirt, and tillage counters that.
Erosion is a serious byproduct of tillage. Bare soil is vulnerable to being swept away by water and wind, to leaching (especially of soluble minerals) and to volatilization (especially of ammonia and water vapor). No-till greatly reduces these.
Tillage requires lots of energy. If done using fossil fuels, it increases the carbon footprint of our operation. Even using muscle power (ours or a draft animal’s) consumes energy, which ultimately increases the carbon footprint (although not necessarily fossil carbon).
Does no-till solve these problems? Bare soil does exist in nature – in severe deserts (not the kind of ecosystem we wish to model) and after some natural disturbance (a washout, grass fire, uprooted tree) exposes the soil. Mother Nature remedies these situations with quick-sprouting, fast-growing plants, mostly annuals and biennials, with seeds that lurk in the soil until a crisis calls them to heal the earth. Most plant species humans prefer for food are in this group too; they are nature’s evolutionary response to disturbed soil.
Conversely, where in nature do we find 4-inch-deep accumulations of plant residues? Rarely, because these materials typically decay as fast as they accumulate. We create such conditions artificially, by importing residues from off-site. Does that mean deep mulches are bad? No, but we should hesitate to call them “natural.” Witness the fact that we have to part that mulch and disturb the soil, however shallowly, to sow or transplant crops.
No-till can be problematic (but not impossible or undesirable), especially as a constant and consistent approach. For example, my own soil was naturally full of rocks. Previous generations removed some to make fields for grazing; but for plant food crops, those fields were still unacceptable. I’ve spent my life (so far) removing those stones – fewer and smaller every year – after tilling, and I expect to continue doing so, as improved yields easily justify the effort. Moreover the soil was badly compacted (by the last ice sheet, I assume, although centuries of cattle hooves didn’t help), and although many millennia of forest cover have improved it greatly, it still requires my intervention to loosen it for food crops. However, that does not mean I must continue tilling indefinitely or frequently. My older, better gardens are mostly tilled by broadfork and wheel hoe, allowing some air and water to penetrate more deeply without accelerating the decay of organic matter. Some of my rotations (e.g. squash > cabbage > tomatoes > corn or grain) allow three or more years without tillage and without added compost or other amendments.
It is impossible not to disturb the soil when harvesting a root crop, although that is qualitatively different from tilling. Indeed few things disturb the soil more than harvesting sunchokes, yet those figure prominently and rightly in many permacrop systems.
A number of systems incorporate no-till principles, and while they offer advantages over conventional tillage, they all pose various problems. Since Edward Faulkner’s 1943 book “Plowman’s Folly,” innovators such as Ruth Stout, Masanobu Fukuoka and Bill Mollison have promoted the no-till concept. Stout’s system is simple: Just add more hay mulch, thus avoiding the need for weeding, fertilizing or soil prep. However, she assumes one can afford (financially or ecologically) to cover a postage-stamp suburban garden with the production of several acres of some dairy farmer’s hayfield, with all the energy consumption involved in that. She also assumes wider spacing than I want for access. In my intensive beds, many crop rows are separated by as little as 8 inches. Try doing that in a 4-inch-plus hay mulch. Also, those people thought mostly of vegetables; my crops include wheat, oats, barley, buckwheat, poppies and flax, all closely spaced and impractical to sow in heavy mulch. Such field crops are also a problem in raised beds. I use intensive wide beds, but not raised; whenever those areas rotate into small grains, I sow the entire plot, including the paths, and raised beds would make that impossible. Methods that work well for mesclun mixes and salsa ingredients are not versatile enough for my larger crop system. Fukuoka’s system (in “The Natural Way of Farming”) includes sowing pelletized rice in the scattered debris of the previous rice crop, not into permanent heavy mulch. And while heavy mulch greatly impedes most weeds, some (witchgrass, chickweed, milkweed, kudzu) adore a heavy mat of grass or leaves. Mulch does make witchgrass runners and some other weeds easy to pull, but they still get out of control quickly.
Perhaps the extreme example of no-till is hugelkultur – covering a mound of brush and rotten logs with a layer of soil or compost. A special advantage of this method is that rotting wood can absorb many times its weight in water, comprising an internal reservoir for the crop in droughty times. Furthermore, decaying woody residues, although high in carbon and low in nitrogen, foster a microcosm of biological activity that sequesters an impressive amount of biologically available nitrogen. I have not tried hugelkultur, but from what I’ve seen, in their first year or two the mounds are most appropriate for larger, widely spaced crops such as tomatoes, peppers and cucurbits; as they mature and settle down, they’re more hospitable to smaller, closely spaced crops such as carrots and onions. Ultimately they decay into humus-rich, ground-level beds where any crop, including grain, can prosper.
While all of these approaches have their strengths, I am skeptical that any one will be appropriate for every crop in every situation. I pooh-pooh some aspect of each while adopting features that seem useful. Like any other system, we must weigh all inputs: the land area supplying mulch and the labor and energy required to collect, process and move it. The real bottom line is often elusive. We may not have all the answers, but we can insist on asking better questions.
About the author: Will Bonsall lives in Industry, Maine, where he directs Scatterseed Project, a seed-saving enterprise. He is the author of “Will Bonsall’s Essential Guide to Radical Self-Reliant Gardening” (Chelsea Green, 2015). You can contact him at [email protected]. Check the Fair schedule for his many presentations there.