Soils—and the biological, chemical, and physical processes they and their interactions enable- provide the backbone of agricultural production and our natural ecosystems. They are the interface between life and death, between living biology and geology. Both human and plant nutrition are rooted in healthy soils. They filter our water supplies and buffer the effects of severe droughts or floods. They help to regulate the Earth’s climate and store over four times more carbon than all of the world’s forests combined. Maintaining soil health is also critical for biodiversity; over two-thirds of the world's species live beneath our feet and more life can be found in a teaspoon of healthy soil than there are people on the planet. As Gershuny and Smillie note, in ‘The Soul of Soil’:
Regenerative agroforestry, therefore, centres first and foremost around the creation and maintenance of healthy soils. It does this through a combination of techniques designed to increase organic soil matter, and thus soil quality, such as using crop rotations, manures, or living manures, and careful management of soil including little or no tillage. In this way, agriculture is both a product of and producer of soil; life makes soil and soil makes more life.
But what does healthy soil look like? And how can we be sure the practices we are implementing are having a positive effect on our soils?
What is soil quality and why we measure it?
Soil quality is defined as the soil's ability to "maintain or enhance water and air quality, and support human health and habitation".
At Mazi, we strongly believe that soil quality is a central pillar of our work, and a system that measures changes in soil quality is necessary to enable us to intimately know our state of soil, enabling us to implement the most appropriate management practices. This knowledge could also be used to feed into research strategies, as well as help inform regional or national policies of best agricultural practices.
How to measure soil quality?
Many attributes of soil contribute to soil quality, and these attributes are all highly interrelated. All processes of soil degradation-compaction, salinization, acidification, loss of biological activity, pollution and erosion should be taken into account when making soil management decisions. This makes things a bit complicated and it is vital that a range of measures should be tested in order to paint an accurate picture of soil health. This can be a little overwhelming, especially for farmers short on time and money.
At Mazi, we have chosen to focus on a few techniques that we are honing with the aim of regularly and consistently recording changes in soil quality as project progresses. Included in our routine health assessment of key indicators of soil quality are:
Infiltration tests - how fast does water enter the soil and how well is the water retained? This is closely related to the soil erosion rates and the porosity of the soil.
Bulk density - regular monitoring of this gives one of the most conclusive indicators of soil tilth and measures compaction rates of soil.
Electrical conductivity - a measurement that correlates with soil properties that affect crop productivity, including soil texture, cation exchange capacity, drainage conditions, organic matter content, salinity and subsurface characteristics.
pH - how alkaline or acid the soils are and what this tells us about plant growth
Nitrate NO3 - Testing for available nitrogen levels
Aggregate stability - the amount of stable aggregates in the soil
Earthworm counts - one of the most universally accepted parameters for soil quality is the number of earthworms that are present
Physical observations - color, soil structure, top-soil depth
Microscope - looking at the biodiversity of our soils and compost under the microscope
We will be updating our website with a more detailed insight into each of these components of our soil tool kit - watch this space for more information!