Good Dirt
March 18, 2011



We’ve been doing a tremendous amount of planting and transplanting in the greenhouse lately - peppers, rosemary, thyme, tomatoes, sage, oregano. So much transplanting that it seems I’ve never had hands or clothes without soil stains on them. So it might seem odd that I would come home, wash up, and then turn around and write about soil. Yet, soil is at the core of everything we do. There’s the saying that if we don’t have our health, we have nothing at all. It could just as easily be said that if we don’t have good soil, we can’t have good health. Why is that?

We live in an unprecedented time, when people have become accustomed to empty calories. We instead pop pills to maintain our health. Whether those pills are pharmaceutical or natural in origin, they still indicate a fundamental lack of adequate nutrition in the foods we eat, which in turn indicates a lack of adequate nutrition in the soil. How have we come to this place? By forgetting that good nutrition comes from the soil. If the soils are unhealthy or devoid of nutrients, our foods will be too. And if our foods are devoid of nutrients, our health cannot be long maintained.

So how do we make and keep the soil healthy? It’s easy to think that soil fertility is simply a question of dumping enough fertilizer on the fields. Many farmers and gardeners are very well acquainted with the big three nutrients required by plants: nitrogen, phosphorus and potassium. Those three elements are so important to plant health that the ratios of N:P:K are listed on every bag of fertilizer sold in this country. If you’ve ever wondered what it means when you see 5-10-5 or 2-14-6 or 12-2-2 listed at the bottom of a fertilizer bag, that is the N:P:K ratio contained in that particular product. But soil fertility, and the resulting nutritional value of the plants and animals grown on that soil, goes way beyond those mere three elements.

While those three ingredients are definitely needed by plants, there is another group of nutrients called the macro-nutrients, which include calcium, magnesium and sulfur. These nutrients are not required in such great amounts as N, P or K, but they are crucial for plant health, and for our health. Poor calcium levels are of course tied to osteoporosis, but if the soils are lacking in calcium, so are the dairy products produced by dairy animals raised on that land. Micronutrients include chlorine, iron, boron, manganese, zinc, copper, molybdenum and nickel. These are required in even smaller amounts, but are again crucial for proper nutrition either in plants, or the creatures that consume the plants. Nutritional deficiencies in any of those will have repercussions in health. And finally are the trace elements such as selenium, iodine, fluorine, cobalt and chromium. Even gold is considered a trace element for some plants, and they don't do well if deprived of it. If we rely on those plants, we won't do well either.

While all this might be fascinating, what relevance does it have for the home gardener or market grower? Plenty. More and more information is mounting from both the research realm and anecdotal experience, which says that soils which are deficient in certain elements will create health problems either in the plants that grow there, and/or in the animals and people who eat them. For instance, many soils in the USA are deficient in selenium, iron and/or copper. These are not generally included in any fertilizer currently available on the market, because they are needed in such small amounts. Yet a lack of iron leads to anemia in adults, and slower learning in children. A lack of copper has also been associated with learning difficulties. A region of the USA deficient in iodine has become known as the goiter belt. Where the soil is deficient in selenium, livestock are prone to being born with white muscle disease, which is a generalized failure of the musculo-skeletal system resulting in loss of strength. Chromium and/or vanadium are involved in the passage of insulin across the cell membrane amongst at least some mammals. If we don't add those elements to the soil, we won't have them in our foods and in our bodies.

Even when we do add them to our soils, the situation gets more complicated. Elements do not act independently of each other. Too much of one can either accelerate or interfere with the absorption of another. So not only do all the elements need to be present in the soils for optimum health, they need to be present in the correct ratios. And finally, as if we didn’t have enough to think about already, those soil concentrations also depend at any given time upon things like temperature, pH, oxygenization and water content of the soils.

So how do we ensure that our soils are made fertile and kept that way? Thousands of pages have already been written about soil health, and I certainly can’t best all those efforts in this brief little blog entry. But I can provide the titles for some good introduction books on soil health and soil fertility:

The Soul of Soil: A Soil-Building Guide for Master Gardeners and Farmers


How to Have a Green Thumb Without an Aching Back: A New Method of Mulch Gardening


Healthy Soils for Sustainable Gardens (Brooklyn Botanic Garden All-Region Guide)


Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web (Revised Edition)




Most of the above books are written for gardeners, rather than farmers, and most of them only address how to get the elements into the soil, rather than the nutritional value of the elements for our foods. Why is that? There are certainly soil science books written for farmers, and nutritional books written for chemists, available through Amazon.com or even your nearest university bookstore. But they tend to run towards the expensive end of the scale, and they often assume you’ve already had your Chemistry 101 and Physics 101 classes. Additionally, the newer soil books address artificial fertilizer use and large-scale delivery systems which are only applicable to growers working at that scale. The newer nutritional books may or may not address natural sources for this-or-that nutrient, but they will almost certainly not address the issue of soil fertility or lack thereof. The above books, on the other hand, are much more affordable, give you a very good understanding about what’s going on in the soil and in the plant, regardless of whether you have a single planting bed or 10,000 acres of wheat. You also don't need advanced science degrees to understand them. And best of all, these books focus on low-cost, low-impact, diversified ways to build robust soil fertility. All in all, reading these books will give you, Dear Reader, a much better understanding of whatever soils you’re working with, and how to improve them, regardless of scale. Improving the soils will then improve the plants you grow there. Improved plant health will very nicely improve your health as well.

I cannot claim to do every last thing recommended in every one of these books. But each year we’re doing more and more of them. Working to build and maintain fertile soil is perhaps one of the highest priorities on the farm, or in the garden, for anyone living from the fruits of their labor. So tomorrow I’ll go right back to my planting, and transplanting, and getting my hands and clothes dirty. And be very thankful for all that good dirt.