Ready, set, grow your own: The importance of well-balanced soil
March 16, 2008
Last week we began a new weekly series on growing herbs and vegetables. The first article, called All You Need Is Love…and a Garden, listed the many reasons to start your own garden. To that list we’d like to add the rapidly rising food prices (feels like a recession to us) and the rapidly diminishing variety and availability of “heirloom” vegetables. According to the Food and Agriculture Organization of the United Nations, since 1900, approximately 75% of the world’s genetic diversity of agricultural crops has been eliminated. Almost 96% of the commercial vegetable varieties available in 1903 are now extinct! We can do our part by planting heirloom seeds, saving the seeds from our harvest, and passing them on to others to grow and enjoy.
You don’t need a lot of space – a windowsill, patio, rooftop, small patch of land will do. You do need good soil. Fellow gardener and soil scientist Michael Astera put together the following information to help get you thinking about the importance of well-balanced soil.
Soil Minerals Simplified, or Why do I need a Soil Test?
There really is no simple answer to questions of soil chemistry any more than there is of blood chemistry. Both require laboratory testing by a skilled technician with sophisticated equipment, and both require a knowledgeable person to interpret the results and make a wise decision based on them.
Why would someone go to their physician and have a blood test? Most likely because they had a problem that was not immediately obvious, even to a trained physician. That is the value of blood tests, hair analysis, spinal fluid tests, DNA tests, bacterial/viral cultures, all of the tools of the medical science laboratory. When they are used properly, in combination with experience and sound judgment, they open a window of information and insight was not available before the modern era. A blood test may show a Potassium deficiency, a hair analysis may show that one has been exposed to toxic levels of lead – valuable insights not easily be gained by simple observation.
It’s the same with soil tests, with the added dimensions that plants not only can’t talk to tell you what isn’t right, but there are far fewer plant or soil “physicians” who have the training and experience to make a diagnosis. In addition, and even more important if one is growing food, you want all of the vitamins, minerals, and nutrients that your body needs. If the proper minerals to make those nutrients aren’t in the soil, they won’t (can’t) be in the plants either.
Ever come across broccoli with a hollow stem, or potatoes with a hollow middle? How about apples with small, brown, bitter-tasting “corky” areas in their flesh? These are signs of Boron deficiency. Boron deficiency and Copper deficiency may also have very similar symptoms in plants: The older leaves look fine, but the new growth is stunted and clustered together. Which is it, Boron or Copper? It’s likely one or the other, but as both are only needed at the rate of a few parts per million in the soil, a few ounces per thousand square feet of garden, it would be very easy to guess wrong and make the problem worse. In most soils, 1.5 to 3 parts per million of Boron is about right and absolutely essential for proper growth; 6ppm may be way too much and can prevent seeds from sprouting or be toxic to plants.
The same is true for the other soil nutrients, though not so dramatically for most of them. If one sees yellowish colored leaves on one’s lawn, the first thought would likely be to apply a Nitrogen fertilizer, and that might work; but there is a good chance that the pale leaves are caused by a deficiency of Sulfur or Iron instead of Nitrogen. A good soil test means one doesn’t have to guess.
Unlike a lawn, if one is growing one’s own food these distinctions may be critical. A lush green lawn, even if it is overdosed with Nitrogen, harms no one. Vegetables grown with too much Nitrogen, though, may well be toxic.
Most of us have noticed that in cow pastures the grass grows lush and green around the fresh “cow pies”. We may also have noticed that the cows graze right up to that lush green grass, but they won’t eat it. That is not because they are so finicky; it’s because cattle have the instinct when choosing their food to know what is healthy and what is not. That lush grass growing on the cow pies is loaded with nitrates that will make them sick.
Many gardeners, even supposedly knowledgeable organic gardeners, judge their produce by how lush and green it is and how rapidly it grows, and they often apply large amounts of high-nitrogen fertilizers, compost, and manure, never realizing that the food they are growing may not be as healthy to eat as it appears. Yes, compost, manure, and humus are critical parts of good gardening, as is a thriving population of microorganisms in the soil, but they are not the whole story and can easily be overdone. What we are talking about here, the soil minerals and their balance is equally important and too often misunderstood or neglected.
Another example: The mineral that the human and animal body requires the most of is Calcium. Calcium is a primary neurotransmitter, it transports nutrients into the cells and goes back for another load, Calcium and Phosphorus make up the latticework of our bones and teeth. Calcium deficiency causes bad teeth, brittle bones, weak muscles, flabby skin. How many gardeners know how much Calcium is in their garden soil? We have all read that green leafy vegetables are a good source of Calcium, but are they? Not if there isn’t sufficient Calcium in the soil. Yet most gardeners, farmers, and gardening and agriculture books don’t even recognize Calcium as the primary nutrient it is, or don’t recognize it as a nutrient at all. If Calcium is mentioned, it is usually along with some mumbo-jumbo about soil pH. Well, one can raise soil pH with lye or with common table salt, or lower it with battery acid, but those wouldn’t be wise moves in the garden. Soil pH is not nearly as important as the mineral balance of the soil is. Get that right and pH takes care of itself.
(As a side note, did you know that Boron is essential for Calcium utilization both in plants and animals? Populations that live in areas with good levels of Boron and Calcium in the soil have a much lower incidence of arthritis and osteoporosis.)
One can’t go dumping Calcium on the garden willy-nilly either without throwing things out of whack. Soil Calcium needs to be in a rather precise ratio to Magnesium and Potassium, that ratio being about seven parts Calcium to one part Magnesium and one part Potassium by weight. Get that right, and most of the rest of the soil chemistry falls right into line, but how could one possibly know how much of any of them was in their soil without a soil test?
Hopefully, you’re starting to see the value of this wonderful new tool we gardeners have. No, it’s not critical to know the mineral balance of the soil for your lawn, or your roses; although they will be at their best if they have all of the needed nutrients, you are not going to be eating them. It is critical if one wishes to feed themselves or their family from the backyard garden.
All of the mineral nutrients needed to balance your soil are available in forms approved for organic growing by the USDA and the various other government agencies worldwide. Most of them are in the form of rock powders such as limestone and rock phosphate; a few are more refined and purified, for example Boron, Copper, and Zinc, which are essential but simply not to be found in a pure enough form from a completely natural source. When you buy a Zinc supplement at the pharmacy or health food store, you are getting this same sort of purified mineral. Various naturally occurring mineral powders such as glacial rock dust and Azomite are also used to provide a source of the micro-trace elements.
Finally, getting a soil test is not an expensive proposition. The cost for a complete soil test that measures 12 different mineral nutrients plus Exchange Capacity, pH, and organic matter content is only $20-$30 US as of the spring of 2008. Go to www.soilminerals.com for lots more information on how to create a perfectly healthy soil to grow perfectly healthy plants to feed perfectly healthy people and animals.
About the author: Michael Astera is a stonemason and woodworker with an abiding passion for science and gardening. He has gardened for many years in the Western USA, and presently lives on a small tropical island where he dreams of growing giant mango trees. Email firstname.lastname@example.org