The living portion of soil is made up of plant roots, and of the numerous microbes and other living organisms that improve soil structure by breaking down organic material.
The recently dead components include deceased soil organisms, green plant material and fresh manures. They decompose readily, and release nutrients quickly.
The very dead portion is humus, the final residue of organic matter breakdown that’s important for soil structure and disease suppression. For fertile soil, all three forms of organic matter should be present at all times.
It's easy to get started to build, restore and grow soil!
In the simplest tradition of organic and natural methods, add a little mulch or compost, and you’re well on your way to make good soil for your homegrown vegetables. In the long run, success in your garden depends on making healthy garden soil. The more you can do to keep your soil healthy, the more productive your garden will be and the higher the quality of your crops…. or so they say, and we are about to find out at Asbury… with the development of our very own crop farm! Some people start with a layer of newspaper or cardboard over a mowed area as a weed barrier.
Good soil care methods imitate natural soil communities. Here we include protecting soil structure, feeding the soil with nutrients from natural and local sources, and increasing the diversity and numbers of the microbes and other organisms that live in the soil.
How so we achieve these goals? Although there are many ways to do this, they all revolve around two basic concepts:
For more fertile soil, you need to increase organic matter and mineral availability
Whenever possible, you should avoid tilling the soil and leave its structure undisturbed
Add Organic Matter for the best soil, sources of organic matter should be as diverse as possible.
1. Add manures for nitrogen. All livestock manures can be valuable additions to soil — their nutrients are readily available to soil organisms and plants. In fact, manures make a greater contribution to soil aggregation than composts, which have already mostly decomposed.
You should apply manure with care. Although pathogens are less likely to be found in manures from homesteads and small farms than those from large confinement livestock operations, you should allow three months between application and harvest of root crops or leafy vegetables such as lettuce and spinach to guard against contamination. (Tall crops such as corn and trellised tomatoes shouldn’t be prone to contamination.)
The Maryland Department of Agriculture (MDA) wants to see more farmers recycle manure instead of buy commercial fertilizer products, and the agency has launched a manure resource page to encourage using the natural plant food. Local farmers have welcomed the new resource the MDA refers to as “Manure Happens.”
2. Try compost. Compost is a means of recycling almost any organic wastes. It reduces the bulk of organic materials, stabilizes their more volatile and soluble nutrients, and speeds up the formation of soil humus. Regular applications of modest amounts of compost — one-quarter inch per season — will provide slow-release nutrients, which will dramatically improve your soil’s water retention and help suppress disease. We recommend using only vegetable matter if you decide to try building a compost heap yourself.
3. Mine” soil nutrients with deep rooted plants. When you first start gardening, it may be necessary to use rock dust, bio-char (ashes from a wood stove) and other slow-release sources of minerals, to correct mineral deficiencies in the soil. In the long run, however, you can supply minerals without purchasing inputs. The organic materials we add to our soil supply most of the minerals healthy crops need. In addition, we can plant “fertility patches” to grow a lot of our own mineral supplements.
Fertility patches include plants that function as “dynamic accumulators.” That is, their roots grow deep, and “mine” mineral reserves from the deeper layers of subsoil, where it has weathered out of the parent rock. The roots of comfrey, for instance, can grow 8 to 10 feet into the subsoil. Stinging nettle is another extremely useful dynamic accumulator. Both nettle and comfrey, in addition to high mineral content, are high in nitrogen. They make excellent additions to a compost heap or can be used as mulches.
4. Plant cover crops. Growing cover crops is perhaps the most valuable strategy we can adopt to feed our soil, build up its fertility and improve its structure with each passing season. Freshly killed cover crops provide readily available nutrients for our soil microbe friends and hence for food crop plants. Additionally, the channels opened up by the decaying roots of cover crops permit oxygen and water to penetrate the soil.
Legumes (clovers, alfalfa, beans and peas) are especially valuable cover crops, because they fix nitrogen from the atmosphere into forms available to crop plants. Mixes of different cover crops are often beneficial. For example, in mixes of grasses and clovers, the grasses add a large amount of biomass and improve soil structure because of the size and complexity of their root systems, and the legumes add nitrogen to help break down the relatively carbon-rich grass roots quickly.
5. Cover the soil with mulch. An obvious way to keep the soil covered is to use organic mulches. Some people advise against using high-carbon materials such as straw or leaves, since soil microbes “rob” available nitrogen from the soil in order to break down the excess amounts of carbon. This is only true, however, 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 won’t be any problem. The mulch retains soil moisture and protects against temperature extremes. Microbes, earthworms and other forms of soil life can “nibble” at the mulch, and slowly incorporate their residues into the topsoil. Actually, high-carbon mulches are preferable for weed control to materials that decompose readily, since they persist longer before being incorporated into the soil food web.
6. Use permanent beds and paths. A key strategy for protecting soil structure is to grow in wide permanent 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 shades the soil surface, which benefits both soil life and plants by conserving moisture and moderating temperature extremes.
You also can use paths to grow your mulches, or mulch the paths and take advantage of foot traffic to help shred or grind 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.
7. Try low-tech tillage. There are almost always better alternatives to tillage, especially power tillage, which inverts and mixes the different layers in the soil profile, disrupts the soil food web and breaks down the “crumb” structure we have worked so hard to achieve. 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. Instead, consider these alternatives.
You can bury the cover crop under a heavy mulch to kill 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 upper ends of the plants as a mulch to help break down the roots more rapidly.
The only time to do massive tillage in the garden is when transplanting a sapling or digging root crops such as potatoes, sweet potatoes and burdock. With such crops, dig deep and thoroughly with the spading fork — the goal, however, is to make such intensive disruptions the rare exception rather than the rule. That way, the intact soil life communities in surrounding beds soon help rebuild the soil food web in the disturbed areas.