If we care for the soil, it will care for us
By Isaiah Ritzmann
Published in March 2021
Soils deserve our attention. This has been one of the most important lessons at the Working Centre’s Market Garden over the past decade. Every year at the Garden as our community plants, weeds, waters, and harvests we have seen how caring for the soil leads to stronger, heartier, more fruitful plants. We’ve learned and explored different methods for caring for the soil. Soil is capturing our imagination. As the power of soil to store carbon is seen as an important way to reduce our emissions. As plants breathe in carbon dioxide through photosynthesis they send down carbon to their roots where it is fed upon by the bacteria and fungi living in the soil. Globally the capacity of soil to sequester carbon is enormous.
Microbiology
We begin with the most important dimension of soil health – the tremendous, largely invisible biological community which inhabits it. Productive soils contain a plethora of living organisms. Some of these are visible to the naked eye: mites, beetles, and earthworms. But most are microscopic, the bacteria and fungi that make the soil their home. And there are a lot of them. In one handful of soil there will be billions of individual microorganisms and perhaps tens of thousands of species. As mind-boggling as it may sound, in one acre there might be anywhere between several hundred to thousands of pounds of these creatures. Many of these are highly beneficial, helping to decay organic matter into nutrients that plants need or humus into enrich soil structure. Many of these organisms congregate in close proximity to plant roots. Through photosynthesis plants will create sugars and proteins they release through their roots in order to feed these critters. In turn these newly expanded populations will work on decomposing organic matter in the soil, producing nutrients (such as nitrogen, phosphorus, and potassium) in plant available form. Some of these creatures are also able to “farm” (so to speak) the soil’s particles – made up of pulverized, tiny rocks – for other needed minerals and nutrients that they pass on to plants. Furthermore, as the microorganisms live, die, and feast they also create gummy substances which help soil particles stick together in “aggregates”. These in turn build soil structure, the next great dimension of the soil.
Soil Structure
Soil structure, it is important to note, is different from soil texture. Soil texture is about the size of soil particles, whether it’s sandy (largest soil particles), silty (medium-sized), or clay (smallest). Soil structure is about how these particles are assembled – do they stick together in “aggregate” clumps or are they dispersed, and in what patterns? Soil structure matters for how healthy the soil is. First and foremost, good soil structure provides a habitat for the soil microbiology. If you harm the structure of the soil, you inadvertently harm the biological population. Good soil structure means there is a lot of porosity in the soil, which means water, air, and plant roots can travel more easily through the soil. This, in turn, can help filter water, provide air for microorganisms, and allow plant roots to find more nutrients and water during a drought. Good soil structure can also guard against erosion, as larger aggregates stay in place more easily. Poor soil structure can do the opposite. Without pores between aggregates the soil can choke-out aerobic (oxygen-breathing) bacteria and be replaced with less helpful anaerobic bacteria. This also decreases the ability of water to filter through the soil. Water then more easily flows over the ground, taking with it the good topsoil and the fertility.
Organic Matter
The third critical dimension to healthy soil is organic matter. At its base organic matter is decomposing plant and animal bodies and excrement in the soil, death which the microbiology turns into nutrients that is then turned into new life by plants. There is a proportional relationship between soil organic matter and microbiology; the more organic material, the more microbes. The organic matter thus serves first of all as a source of nutrients, first for the microbiology and then for the plants. Second of all it serves the whole soil community through its water-holding capacity. It acts like a sponge, being able to absorb about 90% of its own weight in water. In this way plants have access to water during droughts. Furthermore, organic matter helps the soil to clump together, enhancing the structure and preventing erosion. The percentage of organic matter in soils can range from 2-6%. Some studies show that raising organic matter between 1-3% can reduce soil erosion by 20-30%. This is how the microbiology, the structure, and the organic matter rely on and reinforce each other. Some farm practices result in much lower soil organic matter than others.
Soil Fertility
The final dimension of a healthy soil is the importance of soil fertility. A fertile soil – facilitated by the organic matter, the biology, and the structure of the soil – makes it possible to grow plants. Without this plants wouldn’t have the nutrients needed to grow, let alone produce the food we harvest. Yet when the soil is fertile, it doesn’t stay that way. As plants grow, they feed on the nutrients and deplete them in the soil. There are two ways of adding nutrients to the soil either by synthetic fertilizers or natural farming methods.
Presently the dominant form is synthetic fertilizers and this has resulted in dependency of much of our food supply on fertilizers produced with nonrenewable natural gas. These fertilizers feed about one third of the world’s population and account for half of the nitrogen in the human body. Unfortunately, much of this fertilizer doesn’t reach the plants but accumulates in the soil or is washed away into nearby streams or rivers.
Natural Methods of Soil Fertility
Instead of synthetic fertilizers, farmers and gardeners have developed a myriad of ways to return nutrients to the soil: ranging from the spreading of compost and animal manure, to the planting of cover crops (crops planted between harvests). Some leguminous cover crops can actually fix so much nitrogen (by taking it out of the air, and putting it into the soil) that they can supply all the needs of the next planted crop. Most of all when soils have rich microbiology, strong soil structure, and sufficient organic matter, then nutrients will remain in the soil (rather than being washed away) and be available for plants. Then the cycle starts over again, fertility is maintained through composting, manure, cover cropping, and other methods. All these methods help the soil to feed the plants and secures the soil from being washed away.
There is much more to soil than biology, structure, organic matter, and fertility. But these four critical dimensions are the best starting point in our work to honour and care for the soil. They help us understand how our soils have been degraded, here and around the world. They help us understand how healing our soils helps to heal our climate, our waters, and ourselves. Finally, we can see, from the smallest scale of our backyard gardens to the larger scale of our food systems, how caring for the soi
ls can restore them to full health. For untold millennia the work of soil has been intricate, complex, critical, and – in good measure – mysterious. If we do the good work of caring for that which cares for us, it will continue to take care of us – indefinitely.
