Soil Fertility – What is it?

The big success achieved by subsistence gardeners has been their ability to keep producing crops to feed themselves and their communities from the same ground, for hundreds or thousands of years. They employ a system of land management that maintains, or even increases, soil fertility from one year to the next, while at the same time being able to take what they need for themselves. The knowledge of how they managed to do this in a European climate has been largely lost, but will have to be rediscovered if there is to be a sustainable future for human beings on the continent.

The picture is complicated by the fact that in the nineteenth and twentieth-centuries scientific researchers believed that they had unlocked the secrets of soil fertility by analysing the chemical composition of the soil, and working out which chemical elements were required by various crop plants, and in what proportions, in order to achieve maximum growth. Considerable success was achieved by adding specific chemical nutrients to the soil to generate significant boosts in some crop yields. This is the method of crop production still being pursued by the majority of the world’s commercial farmers – which is a major problem, because almost everyone who is not directly involved in the agricultural industry now acknowledges that the science upon which it is based is oversimplified, and gives a misconceived idea of soil fertility.

In reality, soil fertility is an almost infinitely complex subject: mineral content is one component, as is soil type, but it also depends on the interactions of millions, or hundreds of millions of living organisms. Trees, and other deep-rooted plants, play a role in connecting the top soil to the various layers of subsoil – making various minerals available at the surface – and the interaction between tree roots and fungae and other soil organisms helps to maintain ecological stability around areas used to crop production. Organisms such as worms, insects, and small animals, work the soil so that it is well aerated, and well drained, which is a crucial aspect of fertility. Perhaps the most important element in the soil is the microbial life; it appears that bacteria are the planet’s most refined chemists, and are capable of performing almost any chemical reation, with the help of only the most simple ingredients. The most well-known example of this is the ability of some soil bacteria to fix nitrogen from the atmosphere, and make it available to plants. Unfortunately, adding nitrogen to the soil inhibits these bacteria, an example of the harm that can be done through acting on only a partial understanding of a complex subject.

Soil Fertility – How to improve it

The key to increasing soil fertility is to increase the amount of organic material near the surface. Providing that air and water are available, this organic material serves as a food source for the soil organisms, nutrients are released into the soil, soil texture improves, and plants can grow. Over the years, prior to availability of chemical fertilisers, commercial farmers relied increasingly on animal manure to supply this organic matter. Manure from cows, horses, sheep, chickens, etc., is pre-digested plant material, and when spread on the ground, is broken down very quickly by soil organisms, providing a rush of nutrients in the soil, and a strong boost to plant growth. However, it does little to improve long-term soil fertility.

Subsistence gardening, on the other hand, traditionally relies on vegetable compost, mulch, wood ash, straw, etc. Ultimately, vegetable composts provide all the same nutrients as animal manure, but in a slow-release form. The process of digestion takes place in the compost heap, or in the topsoil, and is effected by a myriad of microscopic creatures. These, in turn, support a whole ecosystem of worms, insects, frogs, toads, mammals, and birds, and it is this rich level of biodiversity that ensures that the garden can adapt to day to day changes in conditions, and automatically control the populations of potentially harmful pathogens. This is a process that seems to have the potential to be continued indefinitely. More and more organic matter can be added, which stimulates more microbial activity, more nutrients enter the soil, helping plant growth and funge, but some of the organic material is carried further down, making the topsoil richer and deeper, creating a habitat for more small creatures, and so on and so forth. In modern parlance, the garden becomes a carbon sink; even though organic material is constantly being broken down, and crops are being taken from the garden, the overall amount of organic material in the soil steadily increases, leading to a constant improvement in soil fertility.

Initially, this organic material can come from parts of the garden that are not cultivated. Particularly if one is an inexperienced gardener, it makes sense to start off by cultivating only a small area, and to dedicate as much time as possible to hand-weeding, and getting to know your plants, and how they are adapting to local conditions. The rest of the garden can be left to grow on its own, and cut once or twice a year, with a scythe or a sickle. The cut material can be used as a mulch, or stacked up in a compost heap. If the soil is poor, and exhausted, the growth will be sparse, and the compost will be slow to break down, due to the lack of a healthy microbial culture. But if you persist, growth will gradually improve – grass roots will slowly work their way down into compacted earth, ants will colonise the soil, worms will slowly return, etc. – and the process of decomposition will speed up. The fertility in the cultivated area will increase faster and more dramatically, as more and more mulch is applied, and it will itself start to generate large amounts of material for the compost heap, making it possible to expand the cultivated area, and increase crop production.

People who have only worked in the human-created money economy, find it hard to understand that in the subsistence-garden economy, you really do get something for nothing, and it feels like you are getting something from nothing. The fact that a plant can capture sunlight, combine it with air, water and minerals to create food and fuel, and still have enough left over to create new seeds, and also add extra fertility to the soil, is hard to grasp. The additional fact that the only extra ingredient needed is the work that you do yourself, and that the garden will provide you with the nourishment that you need to do that work, is nothing short of miraculous.