- 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.
When thinking of manure, it’s worth considering our own. Flushing “humanure” away disrupts aquatic ecosystems, and represents a net loss of potential fertility from agricultural soils. On the other hand, human manure requires cautious management to avoid spreading disease. I recommend Joe Jenkins’ The Humanure Handbook, the bible on this subject.
- Try composting. Composting 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.
One is “sheet composting.” In classic composting, you build tall piles in bins, alternating layers of fresh, high-nitrogen “greens,” such as grass clippings, with high-carbon, difficult to break down “browns,” such as dry leaves. Instead, you can keep these two compost materials separate, and apply them in two layers directly to the garden bed.
The moist, volatile, high-nitrogen “greens” go down first, in direct contact with the soil and the microbial populations ready to feed on them, while the drier, coarser, high-carbon “browns” are used as a cover to keep the first layer from drying out or losing its more volatile elements to the atmosphere.
The second alternative is vermicomposting: using earthworms to convert nutrient-dense materials, such as manures, food wastes and green crop residues, into forms usable by plants.
Earthworm castings are a major part of my fertility program. I started vermicomposting with a 3-by-4 foot worm bin. Then last year, I converted the center of my greenhouse to a 4-by-40 foot series of bins, 16 inches deep. My worms process horse manure by the pickup load from a neighbor. Not only do the worm castings feed plant roots, they carry a huge load of beneficial microbes that boost the soil organism community.
- Tap chicken power to mix organic materials into the soil. Typically, I use electric net fencing to manage my chickens, rotating them from place to place on pasture. When needed, however, I “park” them on one of my garden spaces. I dump whatever organic materials I have handy in piles, and the chickens happily do what they love best — scratch ceaselessly through that material, looking for interesting things to eat. In the process, they shred it and incorporate it into the top couple inches of soil, the zone of most intense biological activity. Their droppings are scratched in as well, and they give a big boost to the soil microbes.
- “Mine” soil nutrients with deep rooted plants. As I explained in the previous article, when you first start gardening, it may be necessary to use rock powders, and other slow-release sources of minerals, to correct mineral deficiencies in the soil.
In addition, we plant “fertility patches” to grow a lot of our own mineral supplements. The roots of comfrey, for instance, can grow 8 to 10 feet into the subsoil. Stinging nettle is another extremely useful dynamic accumulator.
- 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. Plus, 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.
- Cover the soil with mulch. An obvious way to keep the soil covered is to use organic mulches.
- 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.
- 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. Above all: use chicken!