Understanding Your Garden's Dirt: Soil Texture and pH Levels

A comprehensive gardener's guide to soil microbiology including pH levels, soil texture, and the best plants for your yard.


| February/March 1998



Layers of Dirt

It is important for gardeners to understand the dirt they are working with.

PHOTO: FOTOLIA/KLIKK

An old farmer told me years ago that it was time to plant corn when it felt comfortable to walk barefooted in the garden. That was right up my alley, as I greatly dislike shoes. Granted, in our modern world of pavement and broken glass it's not always practical or safe to walk without shoes. Ah, but in the garden. When I stand in the garden in bare feet I feel plugged into the earth. It seems as if my feet are communicating with the soil in some way. The soil pushing up against my flat arches and molding to my feet is very comforting ... I would even say mystical but then people would start laughing.

I believe we know more about the surface of the moon than we know about the surface of the earth — not because we haven't tried to understand what is going on immediately under our feet, but because there is so much going on. Soil texture and pH levels vary all across the board, not to mention the rich, complex cycle of decomposition that is constantly in play.

A number of years ago I read a book entitled Soil Microbiology by Selman A. Waksman, Professor of Microbiology at Rutgers University. It is a compilation of research that had been done on soil microbiology up to that time. What I found most fascinating about this book was the frustration the scientists experienced as they struggled to understand soil life by counting microbes. The damn things would change before they could count them. The minute they disrupted the soil by taking a sample or separating elements from it, the soil microorganisms would change.

"The soil is not a mass of dead debris, merely resulting from the physical and chemical weathering of rocks; it is a more or less homogeneous system which has resulted from the decomposition of plant and animal remains. It is teeming with life. The numerous living forms which spend all or part of their life in the soil range from the sub-microscopic viruses and phages, through the microscopic bacteria, actinomycetes, fungi, algae, and protozoa, to the lower animal forms, the worms, insects, and rotifers, many of which can be seen and recognized with the naked eye. These organisms, comprising both the living forms and their dead bodies, as well as the products of their decomposition, such as carbon dioxide and organic acids, interact with the rock constituents to give rise to soil. The soil thus gains the characteristic properties that make it a suitable medium for plant and animal life," Waksman writes in the preface of Soil Microbiology.

As I stand barefooted in my garden there are more individual living microbes under just one foot than there are people in New York City ...and I don't have especially large feet. That is a bit more than I can comprehend. It is time to take Thoreau's advice and "simplify."

Soil Texture: Clay, Sand or Silt?

The simplest way to begin studying your soil is to understand its texture. Rub some of it between a finger and thumb. If it is gritty, your soil is sandy. If it is greasy feeling, you have a clay soil. If you can't make up your mind, you have a silt. All you are doing is putting a name to particle size.





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