Recently I've been researching nutrition (human, not plant), and I've run across many discussions about the benefits of organic foods. I always considered the primary benefit to be the absence of pesticide residue on organically-grown fruit and vegetables, and, in the case of meat, the absence of preventive antibiotics and growth hormones. The nutrition research made me realize the important link between the nutritional status of the plants/animals we eat and the amount of nutrition they provide us. For instance, it should be no surprise that chickens that have access to a variety of plants and bugs to feed upon produce nutritionally richer eggs, and grass-fed beef is nutritionally different from corn-fed beef.
The nutritional impact of organic vegetables may be a little less obvious. That there may be health risks associated with pesticides is fairly obvious. What is not so obvious is the potential impact of non-organic fertilizers on the health of the soil and how this affects the health of the plant growing there. Many farmers routinely add "the big three" (Nitrogen, phosphorus, potassium) to the soil and while these may (or may not) have an immediate beneficial impact in terms of crop yield, it does make a person wonder about the long-term effects on the health of the soil and the bacteria that live there. Plants depend on these bacteria, just as we depend on the bacteria that live in and on our bodies.
In my research into human nutrition, I read that some scientists estimate that bacteria outnumber human cells in our body by a factor of 10 and their genes outnumber human genes in our body by 1000 times. Humans depend on these bacteria, called the human biome, for our survival. Not only do they assist in the digestion of our food, but they make certain vitamins for us that our bodies need but are unable to make. And they are critical to our immunity system. In other words, humans and the trillions of bacteria that inhabit their bodies enjoy a symbiotic relationship: we depend on each other for our survival.
Now back to soil bacteria . . . . While I knew there were bacteria and other microorganisms in the soil, I never thought much about the effect of chemical fertilizers and pesticides on them. Studying human nutrition and our reliance on bacteria has made me more aware and appreciative of the soil biome. Similar to human reliance on bacteria, plants depend on soil bacteria for their survival. Gardeners (at least this one!) are sometimes guilty of adding fertilizers without any evidence that it is needed and no thought for the impact on micro-organisms that live in the soil.
Decisions about food are extremely complicated and my reading on human nutrition has yielded more questions than answers. Although there seems to be more scientifically reliable evidence regarding plant nutrition, we have a lot to learn there as well. What I came away with as a gardener is to be more aware that what we do can have negative impacts on soil health. In the future, I'm going to be slower about reaching for the Miracle Gro or Osmocote or Turf Builder and not use these products out of habit or just because it is typical to fertilize plants in the spring. I'm also going to be more aware that a "balanced" fertilizer (for example, 15-15-15) is not usually a good thing because soils are usually not deficient in all three (nitrogen, phosphorus, and potassium). I'm going to rely more on compost and organic mulches to maintain soil health and fertility and when I think there may be a deficiency, I am going to rely more on a soil test to answer the question. (Click here for a link to soil testing information and forms.) Will I ever use pesticides or chemical fertilizer again? Yes, but I will consider other, more natural alternatives first, and make an effort to use only the amount of chemicals necessary to solve the problem.
For those of you who might be interested, more information on the human biome can be found here and the soil biome here.