“Consider what each soil will bear, and what each refuses.”- Virgil
Your soil is an underlying important aspect to growing healthy and happy plants and gardens. Soil is basically composed of organic matter, various minerals, nutrients, living organisms, liquids, and gases. Soil is the top layer result of a deeper parent material that has developed over time from climate, weather and other biological elements. An important function of soil is to serve as an anchoring mechanism for plant roots. It is also what stores and purifies our water and where a diversity of small organisms and insects live.
I grew up in Illinois where the soil was acidic. In Virginia my first garden was in clay soil. I moved to Alabama where the rocky soil was referred to as chert. And while we lived in New York I got a taste of alkaline soil. And now I am back to good old Virginia clay.
When people ask me how different gardening most be in those various climates I actually respond that the climate was not as much a factor as was the difference in the soils. When I transitioned from master gardener programs, I would always take over again the soil class. Knowing your local soil characteristics is the key to making informed gardening choices in choosing plants and to amend if needed.
As a beginner gardener my solution to every plant problem was to fertilize. Just give it a little juice and it will perk up. Unfortunately this is not a good solution. The root of your plant issues is often in your soil. If you find yourself replacing plants or being disappointed in their growth, take a closer look at your soil and do a few simple soil tests. Amend your soil accordingly and purchase plants that are adapted to your soil conditions for better success. I have found that matching plants to my soil requires a lot less effort, time and money than adjusting my parent soil to grow what I want. One of the most simple things you can do is just look at the color of your soil. Dark brown soils indicate good organic manner and healthy soil. Soils that are red, gray, or yellow indicates low organic matter, drainage and nutrient issues.
To get familiar with your soil you basically need to understand these things: soil structure, soil pH (acid/alkaline scale) fertility (the naturally occurring nutrients and minerals), and soil drainage.
Soil Ph and Fertility (Nutrient Analysis) Test
There is a direct relationship between how readily nutrients are made available to plants based on soil Ph. Adding fertilizers and amendments without knowing your soil Ph can be a costly mistake. You could be spending money on products you don’t need as well as doing more harm than good to your plants and lawn. You can request a soil test kit from your local Cooperative Extension with easy instructions. You basically choose your area to test, dig several small holes, mix your soil (not including the top layer with grass) and send off a sample. Most basic soil tests for home landscapes are very nominal in price ($5-$10). You can also get more detailed results on fertility or nutrient analysis for an additional fee. Most home landscapes do not require regular testing but it is a good thing to do before you begin a garden or when you experience lawn or garden growing issues.
Water Drainage/Retention Test
Most plants do not adapt well to wet soils or dry soils. Find out if your soil holds too much or too little water with the a simple ‘percolation’ test. See Look before you plant landscape trees, a resource from Michigan State University Extension, on how perform this test. Another resource is the Virginia Cooperative Extension publication on Wet and Dry Sites and ways to adapt to these soil conditions.
Improving Your Soil
After performing these tests you will know what, if any, soil amendments are needed. The most frequently recommended amendment is simply organic matter, which can be compost, grass clippings, sphagnum peat among other things.
Note that before you apply soil amendments, many of them will have some effect on your soil Ph either immediately or over time. Also be aware that over applying fertilizers and most soil amendments can have a negative impact on your plants, lawns as well as the environment and water resources. I always feel less is more in terms of amendments and fertilizers.
Here are some resources to help choose soil amendments.
Colorado State University Choosing a Soil Amendment
University of Maryland Extension Soil Amendments and Fertilizers
NC Dept. of Ag & Consumer Science Plant Nutrients
NSW Department of Primary Industries Managing soil amendments and fertilizers for a cleaner environment
Do a quick internet search for plants to match your soil conditions. Your local cooperative extension will also have lists of plants for soil conditions as well as many garden centers. Here are just a few:
University of Maine Cooperative Extension Trees & Shrubs for Clay Soil
Nebraska Extension Plants for Sandy, Dry Conditions
Cornell Fact Sheet on Soil Acidity/Alkalinity Needs for Common Plants
Univ. of Minnesota Extension Best 30 Plants for Tough Sites
So what is the difference between soil and dirt? Soil is alive and dynamic and provides habitat and nutrients to organisms and plants. Dirt is the stuff you sweep up off your kitchen floor.
Happy digging in the soil!
Tracy Blevins, Plants Map
Additional Soil Resources
Cornell Cooperative Extension Soil Basics
University of Missouri Extension Soils, Plant Nutrition & Nutrient Management
Virginia Cooperative Extension Building Healthy Soil
USDA NRCS Soil Health Awareness
USDA Natural Resources Conservation Service: Soils
SoilQuality.Org Soil Quality Management (Joint collaboration of the University of Illinois, Iowa State University, USDA Agricultural Research Service, National Soil Tilth Laboratory, USDA Natural Resource Conservation Service, National Soil Quality Team and National Soil Ecology Branch)
Soil Science Society of America
Virginia’s Soil & Water Conservation Districts