eGarden © 2004 Ed Mues

What's Going on with Our Soils?

There was a passel of red-winged black birds outside my kitchen window both in the maple and at the feeder. The date was March 8. Surely, mild planting weather is close by, only twelve days to spring (equal night and day). With this in mind, I thought it was high time I wrote a column about the state of our soil health, plant nutrition, and some factors beyond our control. Sometimes it's a matter of asking, "Can too much of a good thing, be a bad thing?"

Everyone interested in plants and gardening knows about the main three elements needed for successful growth: nitrogen (N), phosphorous (P), and potassium (K). These three are the most limiting elements related to plant growth, and are, therefore, the most important constituents of fertilizers. N is needed in the greatest amounts for proper plant function. In a nutshell, Nitrogen is needed to produce lush green growth, chlorophyll, and comprises 18% of protein. Phosphorous is important for flowering and fruiting, root growth and development, and plant maturity. Potassium is essential to balance the previous two elements, is needed in starch and chlorophyll formation, adds tone and vigor to plants, and confers some resistance to diseases.

It is much more complex that this, but for our immediate purposes, it's important to remember that plants are a special life form in that they are autotrophs and manufacture their own food. Many people believe that photosynthesis is the most important chemical process taking place on the planet.

So, what good thing could possibly be a bad thing, too? Nitrogen. You'd think it would be blameless, since it's the most abundant element in our atmosphere, nearly 80 %. From this statistic alone, one might suspect plants would always and forever have more than enough nitrogen. Problem is, atmospheric N isn't available to plants (think forests, as well as corn and tomatoes) until it becomes mixed with oxygen or hydrogen and forms nitrates and ammonium, respectively. Soil bacteria and microorganisms that live in the first few feet of our soils, just where the roots of most plants also live, generally perform this natural process.

There, plants are able to absorb the gaseous nitrogen and form the ammonium that they can now use and absorb. Both bacteria and microorganisms become known as "nitrogen fixing" because of this important ability. Many have symbiotic relationships with plant roots, the most famous being the legumes (soybeans, peas, alfalfa etc.). These can add hundreds of pounds of N to a field. Nitrogen is also "fixed" in the soil when we add chemical fertilizer. This, of course, is not a natural process, but a very common one, at home and especially on farms and golf courses. I'll stick to homes and gardens.

Not so long ago, I wrote about the value of snow as a carrier of atmospheric N to earth where it is absorbed by the soil and then fixed as a free fertilizer, courtesy of Mother Nature. Lightning with its intense heat also makes a big contribution by allowing the atmospheric N to combine with oxygen and fall to earth dissolved in rainfall. This is a form of the often heard of "acid rain". Any precipitation that has a pH lower than 5.6 is regarded as acid rain. It is usually a form of dilute nitric acid, and the N can also come from decomposing vegetation and as a by product of blue-green algae which have the ability to fix N. Acid rain can also be a form of dilute sulfuric acid, a result of air pollution from volcanic activity or industry.

Acid rain where we live here in the Catskills is more the norm than the exception. Here is the closer look at...'how too much of a good thing might be a bad thing'. A couple of summers ago I measured rainfall pHs on a regular basis and more frequently than not the pH ranges were between 4.8 and 5.3. There are several negative impacts acid rain has on plants. It clogs leaf stomata (the pores of the plant that allow for gas exchange) and this, of course, interferes with photosynthesis. The dilute acid dissolves and speeds up the leaching of important soil nutrients, in particular K (potassium), Magnesium and Calcium, especially around the root zone.

To add insult to injury, this same process frees aluminum and other metals that hinder the plant's ability to absorb the same three nutrients, now in short supply. The result: Nitrogen begins to build and build, and the other nutrients become less and less available to a point where there is a collapse in the delicate balance necessary to maintain a healthy root environment. Runoff presents possible problems to life in aquatic habitats and to our drinking water. With all the excess N in the soil, we witness stimulated growth too late in the year. This can play havoc with both winter hardiness and pest resistance. Many of these symptoms are visible in the canopies of our forest trees. Look and see.

I am not in favor of doom and gloom commentaries, but just trying to be true to what I think is my mission. I will continue to spell out what I think is going on, and hopefully offer some solutions. As a home gardener, you've probably escaped from some of the larger problems.

Traditional agriculture has promoted the repeated and excessive use of N fertilizers. This has contributed to the gradual, but continued, acidification of our soils. The standard remedy was to lime the soil to correct the too low pH. The result, however, has been the ongoing reduction of the beneficial bacteria and microorganisms, and consequently the plants ability to absorb vital calcium, magnesium and potassium. Several studies indicate this is equivalent to aging the soil at a rate twenty to fifty times faster than normal.

What does this mean? We lose if we allow this state of decline to continue. Check out the following statistics based on a twenty-year study of the nutrient content of our fruits and vegetables. And, bare in mind, this is not just what we eat, but what the animals we consume eat, as well. In the last twenty years the Calcium content has dropped 27%; Iron -- 37%; Vitamin A -- 21%; Vitamin C --30%. Dr. Philip Barak, Prof., Soil Chemistry and Plant Nutrition, University of Wisconsin did this research.

A few of the results of excess N fertilization are manifested in physiological disorders: cracking and bitter pit of fruits; tip burn on leafy vegetables; tomato blossom end rot; browning of cauliflower curds; new growth die back; flower droop on roses; accelerated vegetative growth (here, because the lack of Calcium can't keep up with the water uptake and cell development). Hang in there! It's not all doom and gloom.

A last significant implication in the depletion and rapid aging of soils is also from human activity. Principal among these is the irrigation practice on fertilized ground, and the attendant compacting of soils and subsequent runoff that results from harvesting. These contribute to the deposition and buildup of trace elements in the soil; this further interferes with the smooth function of plant growth. Dr. Barak has suggested that the damage done to our soils in the last fifty years might be equal to thousands of years of normal aging.

Assuming most of my readers are home gardeners, it is probably safe to also assume that excessive fertilization and all the associated problems are not as severe as sketched out above. Acid rain is with us, however, regardless.

This is correctible if the desire is there. If you are the average home gardener (from what I've experienced, most are quite above average, and becoming more organic and environmentally concerned than ever), there is much you can do to safeguard your beds and plots. Putting in smaller raised beds, avoiding unnecessary tilling, and staying out of the beds will go a long way to promoting loose friable healthy soils. Roots will have an easier time penetrating it, as will oxygen and moisture. In all likelihood, yours are in considerably less jeopardy that those of large farms and growing operations. You already have a different respect for the soil than the guy who has to look at the bottom line every day. Maintain that respect and you'll be way ahead of the good practices curve.

From The Garden of Ed. Written for publication April 21, 2004 (not submitted to The Towne Crier).

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