This title appeared in a New York Times article of August 1998. 1 filed it for future reference. When I finally read it I was surprised to find that it did not discuss what I imagined would be there. Instead it started out discussing global warming and carbon dioxide. According to Dr. Tyler Volk, a biology professor at New York University the earth’s soil contributes 10 times more carbon dioxide to the atmosphere than all human activity. We all know from reading that there are beneficial forms of life in the soil but never would we have imagined that their contribution to the atmosphere as a result of the life processes of microorganisms, fungi, worms, bugs, etc., would be so large.
Apart from this aspect it was even more unexpected to come across the statement that gardening may be harmful to the Earth since tillage releases carbon dioxide. Most gardeners assume that a plow, shovel or rototiller is required for a good crop. This raises the question: why do we use cultivation in our gardening? The answer, when one thinks about it is to create a zone where domesticated crops have little competition from other plants. In the past the increase of carbon dioxide produced by small scale tillage was absorbed by plants carrying out photosynthesis. However tillage now is carried on at such a scale that it has become a large contributor to the surplus of carbon dioxide in the atmosphere. So when soil is stripped of its natural cover in order to grow crops, a significant amount of its stored carbon, which contributes to fertility, is lost as carbon dioxide.
Another aspect is that cultivation and compaction destroy beneficial soil fungi. Along this line the beneficial fungi have been increasingly brought to our attention over the past few years. Thus we see articles of vesicular arbuscular mycorrhizae and their beneficial effects.
Gardeners can compensate for the tillage-induced loss of carbon by adding compost and manure, and they can minimize the loss of carbon dioxide from their gardens by experimenting with “no till” gardening. This may be successfully accomplished with a variety of methods, such as: sheet composting (thin layers of compostable materials spread on the soil like a thick mulch) or planting soil improving crops like fava beans or vetch.
Another method mentioned in the article, was to use a deep (I foot) mulch, Assuming this was not a misprint, this method illustrates the dichotomy between a theoretical approach and a practical one which would not violate the theme of the original article-“Do No Harm”. One of the basic tenets of gardening, or most anything for that matter, is to avoid overdoing something. Depending on the material used, the recommended depth of mulch ranges from I to 4 inches, with 2-3 inches being most common for organic material. Deeper than that is asking for trouble, considering all the variables plus the likelihood of attracting undesirable wildlife.
Uncomposted material has a high carbon/nitrogen ratio. Since soil microorganisms require nitrogen in order to decompose the wood, they will deplete the soil of nitrogen, resulting in poor plant performance. Thus, a gardener may have good intentions of conserving water and keeping weed growth down, but by using excess mulch and improper materials, he or she can invite disaster.