24.2: General Approaches

The ultimate purpose of ecological soil management is to create a healthy habitat belowground, with good soil structure, thriving and diverse soil organisms, and nutrients in sufficient supply for high crop yields while not in excess and, as a result, causing off-site pollution. When this is combined with healthy above ground habitat, in the field and around its perimeter, plants are provided with optimal conditions for their growth and protection against pests. Soil health can be improved through six main approaches:

• reducing tillage
• avoiding soil compaction
• growing cover crops
• using better crop rotations
• applying organic amendments in appropriate quantities
• applying inorganic amendments in appropriate quantities, timing and locations

There are many options for making soil management changes in different types of farming systems. We have discussed these in the previous chapters with respect to helping remedy specific problems. A good analogy is to think of your soil as a bank account with credits and debits. The credits are management practices that improve soil health, like manure additions, reduced tillage and cover crops. The debits are the ones that degrade the soil, like compaction from field traffic and intensive tillage (Table 24.1). One farming system may result in a different balance sheet than another due to specific constraints. For example, a daily harvest schedule means that you cannot avoid traffic on wet soils, and small-seeded crops require intensive tillage (at least in the planting row) in order to prepare a seedbed. Still, strive to optimize the system: If a “bad” practice, such as harvesting in a wet field that contains spoilable crops, is unavoidable, try to balance it with a “good” practice, thereby making your soil health account flush. Also, you may have options to reduce the impacts of a bad practice, like controlling traffic to certain lanes to reduce unavoidable soil compaction.

If at all possible, use rotations that use grass or legume forage crops (or a combination of the two), or crops with large amounts of residue as important parts of the system. Leave residues from annual crops in the field, or, if you remove them for feed, composting or bedding, return them to the soil as manure or compost. Use cover crops when soils would otherwise be bare to add organic matter and maintain soil biological health, capture residual plant nutrients, keep the soil protected and reduce erosion. Cover crops also help maintain soil organic matter in resource-scarce regions that lack possible substitutes for using crop residues for fuel or building materials.

Raising animals or having access to animal wastes from nearby farms gives you a wider choice of economically sound rotations. Those that include perennial forages make hay or pasture available to dairy and beef cows, sheep and goats—and nowadays even poultry. In addition, on mixed crop-livestock farms, animal manures can be applied to cropland. It’s easier to maintain organic matter on a diversified crop-and-livestock farm, where sod crops are fed to animals and manures are returned to the soil. Compared to crop farms, fewer nutrients leave farms when livestock products are the main economic output. However, growing crops with high quantities of residues, plus frequent use of green manures and composts, helps maintain soil organic matter and soil health even without animals. In many situations you may have opportunities to bring in organic resources. Perhaps there is a lot of municipal compost available in your area, or maybe a nearby dairy farm sells well-composted manure that can help you grow vegetables or improve an orchard or landscaped area.

You can maintain or increase soil organic matter more easily when you use reduced-tillage systems, especially no-till and strip-till. The decreased soil disturbance keeps biological activity and organic matter decomposition near the surface and helps maintain a soil structure that allows rainfall to infiltrate rapidly. Leaving residue on the surface, or applying mulches, has a dramatic impact on soil biological activity. It encourages the development of earthworm populations, maintains soil moisture and moderates temperature extremes. Adding mulch can be very helpful after you plant perennial trees to control weeds and conserve soil moisture.

Compared with conventional tillage, soil erosion is greatly reduced under minimum-tillage systems, which help keep organic matter and rich topsoil in place. Any other practices that reduce soil erosion, such as contour tillage, strip cropping along the contours and terracing, also help maintain soil organic matter. Even if you use minimum-tillage systems, you also should use sound crop rotations. In fact, it may be more important to rotate crops when large amounts of residue remain on the surface, as they may harbor insect and disease organisms. These problems may be worse in monoculture with no-till practices than with conventional tillage.

Table 24.1 Balance Sheet for Soil Health Management*

Practice or condition	Improves soil health	Reduces soil health
Tillage moldboard plowing chisel plowing disking harrowing conservation tillage	X	XX X X X
Compaction light severe		X XX
Organic matter additions bedded manure liquid manure compost mulch	XX X XX XX
Cover crops winter grain winter legume summer grain summer legume	XX X XX XX
Rotation crops 3-year sod 1-year sod	XX X
*X = a moderate effect; XX = a greater effect.