Soil is a living ecosystem where dead organic matter forms the base of the food web consisting of microscopic and larger organisms. Together, these organisms sustain other biological activities, including plant, animal and human health. Soil supply's nutrients and water, vital for plants, and is home to organisms and bacteria that interact with plants.
In the natural environment, plants form relationships with soil microbes to obtain water, nutrients and protection against some pathogens. In return, the plants provide food.
The use of mineral fertilisers can make some of these relationships redundant, and their breakdown can mean the loss of other benefits such as micronutrients and disease protection.
Certain farming practices, such as tillage (or mechanical digging), is harmful to fungi in soils. These fungi play important roles in helping plants obtain crucial nutrients such as zinc.
Zinc is an essential micronutrient for all living organisms and it is estimated that some one-third of the world’s population is affected by zinc deficiency, widespread in regions that also have zinc-deficient soils. If food staples, such as cereal grains, are grown on such soils and further lack the fungi helper, they will not contain enough zinc. The way food is grown affects the composition and health of plants, and farming practices that focus on soil health could make food more nutritious.
Researchers found that fruits produced under organic farming generally contained more vitamins, flavours such as phenolics, and antioxidants when compared to conventional farming. Many factors are at play here but pest and soil management strategies that benefit soil organisms and their relationship with plants are part of the equation. The composition and function of animals and humans reflects, to some extent, what they eat. For example, the fish you eat is only rich in omega-3 fatty acids if it eats algae and microbes that manufacture these oils, since the fish itself does not produce these compounds.
There are increasing numbers of studies demonstrating the link between nutrition and human health issues. We know, for example, that antioxidants, carbohydrates, saturated fat content and the ratio of omega-6 to omega-3 fatty acids contribute to immune system regulation. We do not produce some of these nutrients; we must obtain them through our food. Therefore, how food is grown is a matter of public health.
Soil is the greatest reservoir of biodiversity. A handful of soil can contain millions of individuals from thousands of species of bacteria and fungi, not to mention the isopods, rotifers, nematodes, worms and many other identified and yet-to-be-identified organisms calling soil home.
Microbes in the soil produce an arsenal of compounds in their chemical warfare for dominance and survival. Many widely used antibiotics and other drugs were isolated from soil, and it may hold the answers to our battle with antibiotic resistance and other diseases, including cancer. It has also been suggested that exposure to diverse microbes in the natural environment can help prevent allergies and other immune-related disorders.