According to the FAO, one in nine people were suffering from chronic undernourishment in 2014-2016. While you’ve already learned about how the dominant messages around hunger leave out the root causes, solutions to human malnutrition often don’t look holistically at the root causes of it either. Often, solutions to human malnutrition focus solely on fixing nutrient deficiency without understanding broader causes. Similarly with soil, we’ve begun treating it as though it were simply a medium for plant growth and a place to apply chemical fertilizer, instead of the wildly complicated ecosystem that it is.
Plants, especially crop plants, require relatively large amounts of nitrogen, phosphorus and potassium. We refer to these as macronutrients. You might be familiar with them; they are the most frequently used inorganic fertilizers in agriculture. To grow, plants also require certain micronutrients in more limited amounts. Plant varieties require different amounts of each of these nutrients, as they have adapted to different habitats and different environmental conditions over time.
As you’ve learned, much of agroecology is rooted in traditional farming systems, which relied on healthy soils. So, let’s look back to history to see why this changed.
The way soil is treated in agriculture changed dramatically in 1840. The German chemist Justus von Liebig promoted the idea that chemistry could revolutionize the practice of agriculture, to increase yields and lower costs. He studied agricultural ecosystems, and articulated what has come to be known as Liebig’s law of the minimum. This law recognized that nutrients were required in specific proportions and a single nutrient in short supply would reduce plant growth. If your wheat plants needed more phosphorus than what was available, the amount of nitrogen in the soil was irrelevant. The nutrient that was limiting plant growth was at its minimum with respect to that growth: thus “the law of the minimum.”
Liebig’s Law of the Minimum
Liebig’s Law of the Minimum inspired the development of chemical fertilizers. Due to the law of the minimum, soil could be provided with specific nutrients, the limiting ones, so as to increase plant growth and eliminate any limiting factors to growth. As a result of Liebig’s law, soil is viewed as a passive sponge through which chemicals pass to roots. Some schools of thought in modern science accepts this view of soil, even though its origin compels it to support and perpetuate the chemical bias in the practice of agriculture.
The chemical bias in agriculture favors synthetic fertilizers and intensive tillage, viewing soils as inert mediums for plant growth. It ignores traditional ecological knowledge, and traditional sustainable soil management practices, in favor of profit-driven agriculture. It also ignores the complex, ecological cycles of soil nutrient replenishment. Read below Mchael Pollan’s take on this moment in history. Here, he references to “Howard”, or Sir Albert Howard, who wrote “An Agricultural Testament” in 1940 in criticism of Liebig.
Excerpt 1: from The Omnivore’s Dilemma
by Michael Pollan
… In Howard’s thinking, the NPK mentality serves as a shorthand for both the powers and limitations of reductionist science. For as followers of Liebig discovered, NPK “works”: If you give plants these three elements, they will grow. From this success it was a short step to drawing the conclusion that the entire mystery of soil fertility had been solved. It fostered the wholesale reimagining of soil (and with it agriculture) from a living system to a kind of machine: Apply inputs of NPK at this end and you will get yields of wheat or corn on the other end. Since treating the soil as a machine seemed to work well enough, at least in the short term, there no longer seemed any need to worry about such quaint things as earthworms and humus [the organic matter in soil].
To reduce such a vast biological complexity to NPK represented the scientific method at its reductionist worst. Complex qualities are reduced to simple quantities; biology gives way to chemistry. As Howard was not the first to point out, that method can only deal with one or two variables at a time. The problem is that once science has reduced a complex phenomenon to couple of variables, however important they may be, the natural tendency is to overlook everything else, to assume that what you can measure is all there is, or at least all that really matters. When we mistake what we can know for all there is to know, a healthy appreciation of one’s ignorance in the face of a mystery like soil fertility gives way to the hubris that we can treat nature as a machine.