Most types of agriculture soil health can be improved through six main approaches:
- reducing tillage
- avoiding soil compaction
- growing cover crops
- using better crop rotations
- applying organic amendments
- applying inorganic amendments
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 23.1). 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 ripe crops that might spoil if you wait for the soil to dry—is unavoidable, try to balance it with a “good” practice, thereby making your soil health account flush.
|Table 23.1 Balance Sheet for Soil Health Management|
|Practice or Condition||Improves Soil Health||Reduces Soil Health|
|Organic matter additions|
If at all possible, use rotations that use grass, legume, or a combination of grass and legume forage crops, 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, capture residual plant nutrients, 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 for use by 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 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 from vegetative residues helps maintain soil organic matter and soil health even without animals.
You can maintain or increase soil organic matter more easily when you use reduced-tillage systems, especially no-till, strip-till, and zone-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. Compared with conventional tillage, soil erosion (water, wind, or tillage) 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 the residue may harbor insect and disease organisms. These problems may be worse in monoculture with no-till practices than with conventional tillage.