Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: WEDNESDAY, October 13, 1993 TAG: 9310130129
SECTION: CURRENT PAGE: NRV-4 EDITION: NEW RIVER VALLEY
SOURCE:
DATELINE: LENGTH: Medium
The lowly soil. We call it dirt, walk on it, cover it with concrete, and have long lost the reverence of our forebears who called it "Mother Earth." Yet from the soil comes our very existence, and where it is rich, life is rich. The pioneers knew this well and let the soil be their guide to locating farms and villages as they spread across the land.
Today few people locate their home because of the soil. We live where we must and in most cases never give a thought to the soil. But for those who love plants, soil must once again be our guide. By understanding a few basics you can be sure to select the plants that will do best in your soil. You can also improve the health, vigor and chances of longer life for your landscape plantings by understanding the nature of soils.
Soil is an unconsolidated mixture of highly complex organic and mineral material. There are the particles, born of the earth's bedrock, sometimes right below where they lay, but more often brought there by water, wind, gravity or glaciers of long ago. Some of the particles are organic, the decayed remains of plants and animals. Together, the particles and the soil chemicals that cling to their surface provide 13 of the 16 elements required for plant growth.
Between the particles water can usually be found, and its excess or scarcity is most frequently the limiting factor in the growth of plants. When the soil is saturated, water fills the large openings, called macropores. As the soil drains and dries, the last of the water defies gravity and clings to the particles through adhesion or sandwiches itself in the tiny micropores, held there - to the benefit of root hairs - by the cohesive attraction between water molecules. When not occupied by water, the macropores are also the passageways that bring life-giving oxygen to roots, a function as essential to plants as the union of air and lungs in humans.
In most healthy soils, the combination of these soil features is approximately 50 percent inorganic minerals, 1 percent to 6 percent organic matter and 44 percent to 49 percent pore space for use by water and oxygen.
Soil is also dynamic. The quantities of water and gas are constantly changing; nutrients are being added from the air and the decay of plant and animal tissue while some are being carried away by the roots of plants or moving deeper into the soil (leaching); and all is in constant, beneficial disruption from the plowing actions of soil creatures. Earthworms alone can move seven tons of soil through their bodies in one year on a half-acre lot!
Soils are highly variable. Their diversity is the product of dozens of physical and climatic factors, all interacting over time to yield the substance that lies under your lawn.
Scientists have identified thousands of soils with specific characteristics, mapped their locations, given them names (loam, silt loam), and described their properties that are either a help or hindrance to farming, plant growth and building activities. This information has been placed in a document called a Soil Survey. It is produced by the USDA Soil Conservation Service, often in cooperation with a state's land-grant university.
For a description of the soils in your area contact your Virginia Cooperative Extension office to obtain the survey for your county. Find your home on the soils map, then read the description of the native soil on your property. You will also be warned of any limitations such as shallowness, lack of fertility, potential for erosion, and a score of other details. This is especially helpful if part of your property includes undisturbed land.
Another source of helpful information is the soil test. In its simplest form, kits and instruments are available from garden stores that allow you to determine the acidity or alkalinity (pH) of your soil. More useful, however, is a complete soil analysis that also tells you not only pH, but the presence of nutrients in your soil, and any that are deficient. Soil tests are done for a small fee by the Soil Testing Lab at Virginia Tech. For information on how to collect and send your samples to a lab, call the Virginia Cooperative Extension Agent in your county.
Joe Hunnings is the Virginia Cooperative Extension Service agent for agriculture in Christiansburg. If you have questions call the Montgomery County extension office at 382-5790.
by CNB