two approaches to soil

The past week has been a busy one at the farm and garden. Thousands of seedlings are eagerly awaiting transfer from the propagation houses to the fields, most of which we are planting by hand. Tomatoes, leeks, lettuces, potatoes, and flowers of all shapes and sizes.

I've decided to write a bit about soil health in this post because of the central role it plays in sustainable farming and gardening practices. This centrality differs from the secondary role soil generally plays within convential farming systems.

Organic farmers and gardeners sometimes say that they are, first and foremost, "growing soil". By this they are referring to the time and effort that goes into fostering soil that is rich in microbially active organic matter and that posesses a healthy structure. In an organic system, the majority of nutrients plants need to thrive are provided by the trillions of bacteria, fungi, earthworms, etc. that break down large, complex, organic molecules into smaller molecules that can be easily absorbed through the plants' root systems. Fertile soil depends on a robust and diverse population of these micro and macro organisms. In order to keep these organisms happy and productive, farmers must "feed" them with organic matter in the form of compost, manure, crop residue, etc. and ensure that there is a sufficient amount of air flow for respiration.

Plants require many nutrients to thrive, but of primary importance are nitrogen, phosphorus, and potassium (the "NPK" listed on bags of fertilizer). Fertilizers are primarily used to provide these elements to plants in simple compounds they can readily absorb through their roots. This gives plants a quick boost which they utilize for rapid growth. In conventional systems, plants receive almost all of their nutrients through fertilizers (the soil having been rendered essentially sterile).

Organic matter that is broken down by soil organisms, on the other hand, releases nutrients slowly over time. There are advantages to this slower route, however. Plants need more than NPK to truly thrive, and decomposed organic matter provides the full range of micronutrients that NPK furtilizers do not. A major reason conventionally farmed crops require so many pesticides is that, even though the plants may look healthy because of their rapid NPK-induced growth, they are too weak to fight off infection because they lack a "balanced diet". NPK fertilizers can also present severe environmental and health problems. Soil can only absorb a certain amount of NPK--the rest is leached into nearby streams or ground water (leading to contamination and "dead zones" in rivers and river basins). Furthermore, the industrial process of fixing gaseous atmospheric nitrogen into a solid form plants like (such as nitrate) requires a tremendous amount of energy. A specialized bacteria that lives in the roots of legumes (beans, peas, etc.) is happy to fix atmospheric nitrogen free of charge, which is why farmers used to plant grops such as alfalfa periodically to replenish soil nitrogen levels.With the advent of chemical fertilizers, however, most conventional farmers have begun to leave their fields fallow during the winter months, which can contribute to the loss of fertile topsoil.

Another component to healthy soil develpment is regular crop rotation. Different plants have different diets, so planting a nitrogen-hungry crop (such as corn) year after year quickly depletes the soil of that nutrient and increases a farmers dependency on fertilizers. Planting the same crop repeatedly also leads to more widespread pest problems. A whole field of the same crop will attract tremendous numbers of pests and increases the chances of catastrophic crop failure. To guard against this, conventional farmers often have to rely on pesticides and fungicides or crops that are genetically engineered to resist disease. All of these recourses have dubious effects on human and environmental health, many of which are not yet fully understood.

A sustainable approach to soil development is undoubtedly more time and labor (and therefor cost) intensive. Unfortunately, many of the true costs of conventional farming are defrayed onto the broader society in the form of government subsidies to farmers, environmental degradation, and public health costs.

The feasability of sustainable agricultural practices on a broad scale is of great concern and importance, and I was delighted to receive an email from my old friend from high school Michael Dickman with the inquiry "why do “sustainable food systems” have to be on a small scale? Couldn’t we make more of a difference if we converted the mass-marketed food supply to sustainable production?" This is a great question to grapple with, and I'm looking forward to putting forth some thoughts in my next post. Until then, be well!