Once you know basic soil types and characteristics, as we’ve outlined in another article, you have several response strategies, and will probably end up using more than one:
- Harvest what already grows, and expand or reduce its extent as appropriate.
- Plant according to soil types and growing conditions you find.
- Till and amend your soil as needed for what you want to plant.
- Mulch to further moderate and protect your planting environment.
Take What the Good Earth Gives You
At the risk of sounding all hippie-dippy, if you have tillable land, there’s a fairly good chance it’s already producing for you. You’re probably familiar with the usual suspects of wild edibles: asparagus, berries, dandelion, mint, mushrooms and mustard, amaranth and arrowroot, cattails and clover, chicory and chickweed, dock and burdock, nasturtium and fireweed, plaintain and purslane, sorrels and cresses, prickly pear cactus in the desert, seaweeds off the shore. These are extensively documented, along with the perils of poisonous lookalikes. Apart from the longer-term benefits of foraging, the presence of these edibles provides you with some head starts in:
- Self-sustenance: Wild edibles provide taste, variety, nutrition and fiber that does not have to be bought, bartered, or trucked in.
- A quick survey of growing conditions: Information about drainage patterns, climate, even soil texture and chemistry, can be inferred from what thrives where.
- Site planning: If kitchen gardening is part of your vision, good growth sites may even factor into where you place a new home. Assessing the soil structure will inform the kind of footing you may need.
Now you can plan your gardens to incorporate or border already thriving patches of edibles and take advantage of what you’ve learned about the qualities of your land. (Note the distinction between incorporating and bordering. You might be able to wrestle a sprawling wild or feral tangle of berries into something more manageable and productive, but not all wild edibles can be domesticated—and some may prefer to be out of the range of even modest agricultural runoff.)
When it comes time to plant, you have at least a couple of options:
- Copy: The very acid soil likely found where heathers, oak, spruce, hickory, chickory, huckleberry, lily, rhubarb, shallots, sorrel, or wild strawberry grow may also accommodate blueberry, celeriac, crabapple, cranberry, eggplant, endive, Irish and sweet potatoes, raspberry, spinach beets, and watermelon. Of course, acidity is only one consideration (albeit a basic one, if you’ll pardon the pun). You must also consider sun and shade, natural hydration and drainage, and other factors.
- Complement: One introduction to the various kinds of complementary or synergistic planting systems—intercropping and other forms of polyculture—is the American Indian tradition of “Three Sisters” companion planting:
- Living cornstalks support climbing bean plants.
- Beans replenish nitrogen for the corn and squash.
- Squash leaves reduce evaporation, suppress weeds, and repel pests.
- After harvest, beans provide amino acids lacking in corn, enhancing corn’s nutritive value and the body’s creation of proteins and niacin.
Diverse Native American cultures have adapted the method for poor soil and arid climates, and may include a fourth sister, the Rocky Mountain bee plant, to encourage pollination.
Tillage and Amendment: Give Your Soil Some Space and Create Good Chemistry
Soil for cultivation needs about 50 per cent of its volume to be open “pore space” for water and air to circulate, and for roots to spread and thrive. Tilling (turning over the soil as needed) breaks up compacted soil and creates pore space. If your soil contains too much clay or silt, it will be hard for you to work, and will make your plants work harder, too (but not better!). Clay- or silt-heavy soils can be amended during tilling with medium to coarse-grained sand to improve water absorption and drainage, as well as air circulation. Amendment generally means adding substances to the soil, typically non-nutritive, meant to alter the soil’s texture or chemistry.
Loam, the overall best soil type for planting, is defined by the presence of humus—organic matter whose decomposition has reduced it to a stable (inert) state. Humus is primarily carbon; it’s measured by weighing the soil before and after burning it away. Despite its organic origin, meaning it’s the residue of living things, any nutritive matter it may contain is generally unavailable to plants. Humus can be approximated by stable natural compost or mature cultivated compost, sometimes called effective or active humus. Compost may transfer some nutrition to your plants, but that’s incidental to its primary benefit of improving soil texture so that it allows the free exchange of air and water. Be sure to do your research and know exactly what state of decomposition organic material needs to be in before you add it to your soil, lest you just create mold nurseries and pest magnets.
Amending the chemistry—acidity or alkalinity—of your soil is fairly straightforward. Lime (calcium carbonate) is used to alkalize acidic soils. Various slow- or fast-acting forms of sulfur acidify alkaline soils. Woody content in compost or mulch also has an acidifying effect.
Conserve and Protect
Mulch covers a multitude of sins. More precisely, it covers your planting areas to enable you to control evaporation and suppress weeds, and has a number of other uses. Some mulches decompose on site to provide compost when their mulchy work is done. Others are more inert, and get moved around and re-used with changing seasons and weather, or plowed under during tillage. In “Three Sisters” agriculture, the squash leaves form a kind of living mulch. As always, do your homework: generally, for example, you’ll keep mulch a little clear from your plantings’ stem-root juncture, but some plants are grown with a little mulch piled around their base.
Special Cases: the Good, the Bad, and the Ugly
Nature is infinitely varied, of course. Here are just a few of the exceptions to the taxonomy and strategies we’ve been examining.
Loess soil is an especially fertile, yellowish, silty soil that defies the usual categories. Its seemingly erratic placement around the world—it was once thought to exist only in China and the Missouri Valley—led to the belief that its deposits were windblown. As more deposits have been discovered, current thinking maps them onto periods and locations of glacial melt in the Earth’s past.
Chalky or basic soil contains a high level of nutrients. However, “basic” here is used in the sense we heard it in chemistry lab: the opposite of acidic, that is, alkaline. Its high porosity can be corrected by humus, but few plants can thrive in that level of alkalinity.
Caliche is a kind of soil cemented into hard layers by lime (calcium carbonate). Yes, this is the same stuff you use to alkalize acidic soil, but in the form of big clumps or extensive plates. At its worst, it is no better a growth medium than concrete; as with concrete, if you want to grow anything normally, it needs to be removed. A shallow surface layer might be broken through with a pickaxe, but thickness can run up to several feet either on the surface or in successive underground layers. Even if broken through for planting, it restricts root growth, inhibits water transfer, and alters soil chemistry. Arizona’s Cooperative Extension Service proposes a workaround involving both clearing space for each planting and drilling drainage “chimneys” to improve water circulation. Large plants require large excavations (remember that a tree’s root structure typically mirrors the above-ground extent of the tree). The smallest plants are better off in raised beds, and shrubs might work best in some hybrid arrangement of raised bed and excavated ground.
Other articles in this issue: