Good soil quality is the foundation of all gardening. Experienced gardeners like to say that you “feed the soil, not the plant.” Healthy soil requires preparation and maintenance, but takes out a lot of the guess work of “what went wrong?” later on! When you prepare an in-ground garden (not raised bed) for planting, the first thing you need to do is assess the quality of your soil. During the early stages of garden planning, you should conduct a soil test.
Soil test kits can be picked up from the NC State county extension office. Follow the instructions and mail it off for testing. The test is free, but be patient on getting the results.A soil test will give you information about your soil composition and toxicity levels, which is particularly important in urban settings where your location may have been used for other purposes in the past.
All soils are made up of a combination of three basic components: clay, sand, and loam. Your soil also has a specific ratio of nitrogen, phosphorus and potassium (N-P-K). Good quality soils have high quality organic materials, good aeration, and the ability to hold just enough moisture.
While the soil test is essential, you can tell a lot about your soil simply by looking at the color and holding it in your hand. A high quality soil will be a dark rich brown to black, light, somewhat crumbly in your hand, and a velvety (or loamy) feel when you rub it between your fingers.
When we think about a garden, we tend to focus on the tasty vegetables they produce, but our soils are teeming with life! In one gram of healthy soil (about the weight of a standard paper clip) expect to find these critters:
All of these forms of life are useful in breaking down organic matter and providing nutrients, which is why we choose organic and non-synthetic soil amendments. Amending the soil with chemical fertilizers will kill your soil life and affect the health of your plants.
If you are planning an in-ground garden here in the South, it’s a pretty fair bet that you have clay soil that will take a little effort to prepare before you are ready to plant. The biggest problems with clay soils are excess water retention and compaction. To improve the texture of the soil and promote better drainage, the best thing that you can add is compost and other organic material. While adding some sand is okay, too much can backfire by making your soil drain too quickly.
If the site has good drainage and the soil is workable, prepping the soil involves adding about 1-3 inches of compost (or composted manure) to the soil when the soil is first turned.If the soil tests indicate low pH (highly acidic), add lime at the same time you add compost. Do not add fertilizer and garden lime at the same time.
We also recommend adding these organic (made from plants, animals, and rock) soil amendments as needed: plantone, blood meal, and bone meal. Each adds different nutrients to the soil. Bone meal adds Phosphorus, blood meal adds Nitrogen, and plantone is an organic fertilizer mix that adds N, P and K.
Annually, gardeners can add up to 1 inch of compost to plots using simple hand tools. Remember that with harvest, nutrients are taken out of the soil. With each new planting and depending on which plants are going in, add fertilizer. Every three years gardeners should test the soil, adding lime and other nutrients as needed.
Mulch is a great addition to the garden for keeping weeds under control, protecting the soil and retaining moisture. Organic matter is best (leaves, straw, wood chips), but newspaper and cardboard also work well. The mulch layer doesn’t have to be large; 2-3 inches is very effective. Be sure not to exceed 4 inches.
If your soil is beyond hope or you are gardening with a population who would benefit from easier accessibility, another option is to create raised beds that sit on top of your existing soil. The easiest way to prepare the soil in raised beds is to purchase topsoil and compost or planter mix. Avoid falling into a false sense of security about your soil: Raised beds, like conventional beds, need to have regular soil maintenance.
Add a ½ inch layer of compost annually and fertilize with each new planting to maintain soil nutrients. Be especially careful not to over-fertilize in containers and raised beds. Also, be on the watch for signs of soil compaction, nutrient depletion, or disease, such as stunted plants.
For a quick and fun soil check, have kids dig out of the garden a cube of soil about one foot on a side and count how many worms and bugs are in it. Compare with another area of the garden or an area of the yard. Record and test at the beginning of each season.
Credits: Materials drawn from N.C. State’s Cooperative Extension and Community Food Gardening Manual for North Carolina by Don Boekelheide, Dr. Lucy Bradley and Dr. Keith Baldwin, draft version March 2010.
By Henry Owen with assistance from Kathy Metzo and Carol Adams