Lesson

4. Linking Soil Health and Human Health

In this course so far, you’ve gone from learning about broad global systems to more specific ecological systems and agroecosystems. Now, in this Lesson you will explore the micro systems of nutrients cycling in the soil and in the human system. You will also explore how human health and nutrition is inherently linked to the soil’s nutrition, while keeping in mind the broader systems at work in global agriculture.

As our diets have simplified, so have our farming practices. Instead of treating soil as the dynamic, living ecosystem that it is, it has been reduced to a (often sterilized) medium for plant growth, supplemented by synthetic chemical fertilizers. We have over-simplified how we think about both soil and human nutrition, and moved towards supplying macronutrients and energy without consideration for the micronutrients or microbial balance needed to ensure a healthy system.

Unlike humans, who rely on plants and animals to provide our energy requirements, plants acquire energy in the form of glucose, carbon and oxygen from photosynthesis. But just like humans, plants need nutrients, containing crucial elements and compounds in order to function. These micro- and macro-nutrients are necessary for forming plant structures, photosynthesis, and metabolism. These nutrients also play a part in maintaining water balance inside the plants, and allow the plant to absorb ions from the soil. Without these essential nutrients, plants suffer, and struggle to be productive or protect themselves from pests. Humans, in turn, rely on plants to get much of our nutrients.

Organic soil fertility management is guided by the philosophy “feed the soil, not the plant.” Nutrients flow in cycles, from the biotic components of ecosystems, to the abiotic components and back again. These cycles are known as biogeochemical cycles. Some nutrients are involved in these cycles on a global scale, while others take place at the level of the agroecosystem. As you learned, farmers remove energy and nutrients from the agroecosystem in the form of crops. In thinking about sustainable agroecosystems and soil nutrition, it is important to recognize that those nutrients need to be replenished in some way.

In this Lesson, you’ll take a careful look at how soil nutrition and human nutrition are linked to the global shifts in our agricultural systems, as well as delve into more practical learning around plant nutrients and agroecological practices to manage soil fertility.

Learning Objectives:

  1. To compare how the simplification of diets is related to industrialized agriculture and a globalized food system.
  2. To be able to describe global nutrient cycles, differentiate between plant macronutrients and micronutrients, and the science of plant nutrition.
  3. To identify different nutrient deficiencies, and know the source of plant nutrients.
  4. To understand how agroecological practices manage long-term soil fertility, and how industrial farming practices manage short-term soil fertility.