Be Soil Aware! by Catherine Kavassalis October 2008 Soil . . . scoop up a handful of the magic stuff.   Look at it closely. What wonders it holds as it lies there in your palm.  Tiny sharp grains of sand, little faggots of wood and leaf fiber, infinitely small round pieces of marble, fragments of shell, specks of black carbon, a section of vertebrae from some minute creature.  And mingling with it all the dust of countless generations of plants and flowers, trees, animals and – yes – our own, age-long forgotten forebears, gardeners of long ago.  Can this incredible composition be the common soil?-   Stuart Maddox Masters, The Seasons Through (1948)

October is the start of a new growing season. It is time to add new perennials and divide old ones, to plant spring bulbs and most importantly, it is time to care for your soil. Just how is your soil? Is it acidic, neutral or alkaline? Is it nutrient rich or is it missing something? What is the structure and texture of your soil?

From the germination of seeds, to root formation, to absorption of nutrients, the right soil is critical for healthy plants. Soils are admixtures of sand, silt and clay. These particles aggregate in particular ways due to their size, shape and chemical composition creating a characteristic soil structure. Soils can be structureless (single grained), granular, crumby, platy and blocky, etc. Soils with different structures have distinctly different properties with regard to such things as water infiltration and percolation, gas exchange, nutrient retention, compaction, freezing and thawing, and biological activity.

Most plants do best with a granulated or crumby soil structure made up of mineral and organic matter of various particulate sizes. Clay and sandy soils can be improved with such things as compost, peat, bark, wood chips, animal manures, and green manures. These amendments improve soil structure and the availability of nutrients.

There are six macronutrients including the big three found in most fertilizers: nitrogen (N), phosphorus (P) and potassium (K) as well as calcium (Ca), magnesium (Mg) and sulfur (S). These macronutrients are required in large quantity by plants and are necessary for many cellular functions. Equally critical are plant micronutrients including iron (Fe), manganese (Mn), boron (B), copper (Cu), molybdenum (Mo), nickel (Ni), chlorine (Cl), and zinc (Zn). Though smaller amounts are needed, they are just as necessary. For instance, iron is need for the production of chlorophyll molecules - the green pigment responsible for photosynthesis (sugar production). Symptomatic of iron deficiency, are yellow leaves with a network of dark green veins, a condition termed iron chlorosis.

Sometimes our plants give us symptomatic clues that something is missing. Generally however, we don’t know much about the chemistry of our soil. There are kits you can purchase to do a home soil analysis. These can tell you a bit about the big three: nitrogen (N), potassium (K) and phosphorus (P) as well as pH, though they may not be too accurate. You can also send a sample off to a laboratory like the University of Guelph’s Soil and Nutrient Laboratory (519-767-6299 or info@lsd.uoguelph.ca). For $35 you can learn your soil pH, the big three as well as magnesium, total salts, organic matter and recommendations for lawn and garden. Additional tests are of course more money.

Learning the pH of your soil can aid you in the selection of plants and your choice of soil amendments and mulches. For instance, if you want to grow rhododendrons and your soil is alkaline (pH larger than 7 (more OH- than H+)), you will have troubles. Rhododendrons (and many members of the Ericaceae family) evolved in acidic soils where elements like zinc, aluminium, iron, copper, cobalt, and manganese were easily accessible. These nutrients are not soluble in more alkaline soils and many acid-loving plants do not have the necessary morphology and physiology to absorb them. If you have soil like mine which tends to the alkaline, you might see your rhodos develop iron chlorosis. There may be iron in the soil, but it just isn’t available to the plant. To solve this, the soil can be made more acidic by the addition of sulfur, aluminum sulfate, or iron sulfate. Better still add acidic compost made from oak leaves, shredded pine bark, decaying wood chunks, etc.

Amending your soils with quality compost and appropriate mulches is the best ways to improve the overall quality of your soil. The right soil for the right plant is the key to successful gardening. So get to know your soil this fall and give it a little extra attention to start your new gardening season off right.

May toads nestle in your flower beds and help you tend your beauties in the spring.
 

Notes:

Check out my soil texture experiment