Most gardeners understand that good soil is foundational to good growth. But it may surprise some to know that the soil we live on is very much alive, dynamic, and part of a highly complex ecosystem. What some refer to as “dirt” is actually one of three actors in a three-part food web along with soil organisms and plants. While the minds of most turn to thoughts about planting when the weather turns cooler, it is equally timely to learn more about your soil and prepare it for next year.
How well your plants, trees, and turf grow depends on the interaction of certain factors that affect your soil. These include the soil’s pH, available nutrients, water and oxygen permeability, temperature, and light. While heavy metals are more readily available at low pH, most nutrients are at their peak availability when the soil is at a neutral or near-neutral pH level. An annual soil test is the surest way to learn the current health status of your soil, and it should always be the first course of action. Soil tests will reveal nutritional deficiencies or any toxicities as well.
Generally, soil is divided into two types based on the amount of organic carbon: organic soil (20% or more organic carbon) and mineral (less than 20% organic carbon). Not surprisingly, Georgia soils are predominantly mineral. All soils are formed in layers, or “horizons,” and establish certain textures that are classified based on of varying amounts of sand, silt, and clay. (These classifications do not apply to organic soils). Texture, along with particle size, density, and porosity (pore space), affect the structure of the soil and the ability of air and water to move within it. Soil organisms also are affected by these characteristics.
Soil organisms are the second player in this unique relationship with plants. Bacteria, fungi, protozoa, nematodes, and earthworms serve important functions in the soil. These hidden workhorses are dependent on a certain balance among soil pH, nutrients, water, oxygen, temperature, and light. Most prefer a neutral pH, since more nutrients are available at this state, though fungi are acid tolerant. Soil organisms are the prime mover of nutrients throughout the soil. For this reason, soil porosity is important. Yet, most organisms are microscopic and rely on larger organisms to move them about. The earthworm is an exception; it can make its own soil pores, which is why they are so valuable to the gardener.
So how do plants fit into this food supply triangle? Naturally, plants rely on the right balance of soil pH, nutrients, water, oxygen, temperature, and light. These factors are referred to as “abiotic” or non-living. There are, however, “biotic” factors involved, which describe the complex relationships between and among plants and organisms.
Healthy soil is not only a prerequisite for good growth, but it also prevents many common problems. In addition to an annual soil test, many farmers and gardeners find that keeping a journal about the weather, insects, and other natural events is useful way to keep track of what is happening in the environment. Since most of Georgia’s organic matter has been lost to erosion over the last 200 years, regularly adding organic matter back into the soil is an essential measure; amending should be done early and to a depth of 8-12 inches to give nutrients time to get worked in. Though it requires a commitment of time and space, composting is a sustainable and longer lasting amendment than fertilizer alone. Composting not only adds nutrients, but improves soil composition, water retention, and root development. Better still, compost attracts beneficial organisms.
Amy Rhoads, the author of this article, is a Paulding County Master Gardener Extension
Volunteer with University of Georgia Cooperative Extension. For more information, or assistance with soil testing, please contact the UGA Extension Paulding County office at 530 West Memorial Dr. Dallas Ga or call, 770-443-7616.
