Soil health management can be distilled to two principles:
- Maximize photosynthesis
- Minimize tillage
These are principles; they do not tell you what practices you should use, but rather what the practices you choose to implement should provide.
Maximizing photosynthesis is all about interception of sunlight to power plant growth.
Fill the space you have with plant growth. Aim for a full-time, full canopy as much as possible.
Fill the time you have with plant growth, year-round plant growth, although I doubt we could tell if you missed a couple weeks over the course of a year.
Filling time and space will require a soil with sufficient nutrients, optimum pH, and structure conducive to seedling emergence and to root growth, which brings us to the second principle.
Minimizing tillage is all about maintaining soil structure and keeping the soil protected from erosion. Tillage damages soil structure and reduces protective residue cover.
When both principles are followed, you get the five soil health principles and practices from NRCS, regenerative agriculture, and others:
- Keep soil covered as much as possible. This is achieved by combining the Max and min principles.
- Minimize soil disturbance. Tillage is the primary culprit in disturbing the soil, hence the min principle.
- Keep plants growing year-round. This is one way to accomplish the Max principle.
- Use cover crops and crop rotation. These practices also accomplish the Max principle.
- Integrate livestock grazing. This practice allows more flexibility in applying the Max and min principles, allows the use of perennials, and reduces tillage.
The Max and min principles together produce a soil with the organic matter concentrated at the soil surface, where it can do the most good.
The flow of carbon through the soil is nearly continuous, both from plants and from decaying crop residue.
In the long-term, and sometimes in the short-term, these two principles should address real soil problems.
These principles fit with the current views of soil organic matter and soil biology.
Cover crops, either monoculture or mixtures, can be used with cash crops to maximize photosynthesis. Achieving the Max principle in annual crops will be easier with crop rotation.
Green manures show the trade-off between the two principles; photosynthesis is maximized by producing big biomass, but tillage is involved. Green manures can, it seems, provide benefits in some cropping systems that cannot be achieved with practices that abide by both principles. However, a sufficient amount of biomass must be produced for them to be beneficial.
Minimizing tillage is much easier with herbicides. They are the easy choice over tillage and have little if any effects on soil biology.
Finally, these two principles can incorporate the essentials of sustaining agriculture production. They assume that erosion has been minimized; why improve an eroding soil?
Of course, it’s not simple. These principles must be adjusted for many factors: climate, markets, economics, crops, pests, soils, regulations, equipment, technology, etc. and all the inherent trade-offs of agriculture. And these principles assume that erosion, which is the opposite of building soil, is minimized. You cannot build health into a soil that is being eroded.
That’s it, two principles.