5 Soil Health Principles
Soil health, plant health, and keeping the planet habitable come down to having healthy soil biology. The components of soil are Physical, Chemical and Biological but for decades we have not concerned ourself with the Biological. The diversity of biological life in ours soils is astounding, making up about nearly half of the planet's biodiversity. The story of our agriculture is in many ways a story of war on this diversity in conjunction with our war on soil organic matter. The story of our future agriculture has to be about turning that around.
The 5 Soil Health Principles are for land stewards to follow in order not to be at war with this diversity and thereby the functioning of the soil-plant ecosystem. They are all aimed at building healthy soil biology. These 5 principles can be applied to almost all types of farming and in almost all contexts. These days Context is often included as a 6th Principle but this post focuses on the 5.
1. Minimum Disturbance - to put it simply don't break their house, don't smash it with ploughs and spades. We need to minimise soil disturbance. For 10 000 years ploughing has been an integral part of farming and for 10 000 years we have bean breaking up the structure of the soil and breaking all the fungal mycelia that provide the communication network for life underground. In addition to this disturbing of soil also accelerates the combustion of soil organic mater into CO2, moving carbon from the soil into the atmosphere.
Aside from this Physical Disturbance there is also:
Chemical Disturbance - the application of pesticides and synthetic fertilisers similarly wrecks havoc with soil biology, causing significant declines in population and hampering its ability to perform its vital tasks. Burning of organic matter - grass and residue - is also a form of Chemical Disturbance.
Biological Disturbance - overgrazing and monoculture are ways in which we biologically disturb our soils. Both of these decrease the diversity and function of soil biology.
2. Keep it covered - healthy soil is a living entity and it needs a skin to protect it from the sun, the wind and the rain. Aside from the massive problem of soil loss due to erosion, the temperature swings of bare soil also kill soil biology. Our soils need to be covered in a skin of mulch and living plants to ensure healthy soil biology. For too much of the year our agricultural fields are left bare and most of our orchards and vineyards are kept bare of all other plant life all year round. In addition all this bare soil is highly detrimental to the small water cycle, which ultimately translates into less localised rainfall (see the Soil Carbon Sponge).
3. Diversity - diversity is nature's system of resilience. Plants grown in mixed family groups out perform mono crops, are more resilient to drought, more resilient to pests and more resilient to disease. Diverse plants not only access different parts of the soil they also work with different microbial communities to access different minerals and nutrients from the soil. Above ground diversity translates into below ground diversity. These benefits are not just for the plants themselves, via fungal pathways they are made available to the other plants growing with them. This soil biology needs a varied diet, which can be provided by crop rotation, intercropping and the use multi-species covers. In addition to this pollinator areas, trees and hedges provide more diversity and other benefits.
4. Living root - soil biology is primarily fed from the root exudates of plants. So important is soil biology for plants that they contribute up to 40% of the sugars they produce to feeding soil biology in exchange for nutrients and water. If you don't have a living root in the ground your soil biology is not being fed. Most row crop fields around the world have a living root in the ground for only 4 months of the year. Cover crops are crucial for extending this period .
5. Incorporate animals - all farms used to be mixed farms and animals, especially cattle, sheep, goats, chickens and pigs, were crucial in maintaining farm fertility. Animals are mobile bio-digestors that rapidly produce nutrient rich compost (dung and urine), taking plant material that is not available to soil biology, breaking it down and making it available. This stimulates the soil biology, enhancing the function of the soil-plant ecosystem in fields. With the advent of industrial agriculture we removed the animals from the fields and confined them, replacing the nutrient cycle they used to stimulate with synthetic fertilisers. Managed livestock need to be returned to cropping and horticultural systems.