soil test

In South Carolina Low Country kitchens, there is an inviolate rule when it comes to making shrimp and grits: Start with good shrimp. What does this have to do with gardening in Western North Carolina? Everything. To make a healthy, productive garden, start with good soil. 

What is good soil?
Think of soil as a mixture of solid material (minerals and organic matter), air, and water. The ideal soil contains 50 percent solid materials, 25 percent air, and 25 percent water.

Plant nutrients
Healthy plant growth depends on 18 nutrients in this mix. The primary nutrients include carbon, hydrogen, and oxygen, as well as nitrogen, phosphorus, and potassium. Secondary nutrients are calcium, magnesium, and sulfur. Micronutrients are iron, chlorine, manganese, boron, zinc, copper, molybdenum, nickel, and cobalt. 

Fertilizers
Think of fertilizers as supplements. There is no substitute for starting with well-balanced soil, but fertilizers can provide elements that may be lacking in the soil and can stimulate plant growth. All fertilizers, synthetic or natural, slow or fast release, are labeled with three numbers:

• N for nitrogen, responsible for foliage growth and color;
• P for phosphorus, which promotes early root growth and the production of flowers, fruits and seeds; and
• K for potassium, which helps with hardiness and disease resistance.

Use a soil test to determine what nutrients your soil may need. For more information about soil testing, see https://www.buncombemastergardener.org/testing-soil-advantage-free-testing-december-1-soil-sample-form-gardeners/.

Regardless of what kind of fertilizer you use, be sure to read the directions, use the proper proportions, and follow the manufacturers’ safety guidelines when applying.

Amendments
Compacted soil has too little air. Poorly drained soil holds too much water. Adding organic matter can help remedy both. North Carolina Extension soil specialists recommend adding about 2 inches of organic matter—compost, manures and pine bark (less than ½ inch in diameter)—to make up about 25 percent of the top 8 inches of your garden soil. For clay soils, they say composted leaves (leaf mold) and pine bark are best—they do NOT recommend hardwood bark, peat moss, pine straw, sand, or wood chips.

Putting it all together
When soil texture and nutrients are in the right balance, plants, beneficial insects, and bacteria thrive. Think back to that bowl of shrimp and grits. We’ve got fresh and flavorful shrimp, but what about the grits? The best grits are smooth and have a consistent texture. The same holds true for soil.

This means removing clods of clay and breaking up large clumps of dirt. The amendments and fertilizers are evenly distributed. Like a cake batter, your ingredients are well-mixed. Finally, rocks and debris are raked out and removed. The product is a luscious soil that is easy to turn, well-drained and rich in the elements that create a welcoming environment for your garden and all the organisms that support it.

Worth the work
When the days lengthen and temperatures moderate, our heads fill with spring dreams of fresh lettuce, rosy radishes, and sugar snap peas.  But before putting a seed in the ground, think of shrimp and grits. Work from the ground up: test the soil, then (like a good cook) add the necessary ingredients to make your soil the best it can be. It’s time well spent and your garden will show its appreciation all year long.

Article written by Janet Moore, Extension Master Gardener Volunteer.

Resources
Useful NCSU Extension publications include:
“Soils and Plant Nutrients”
https://content.ces.ncsu.edu/extension-gardener-handbook/1-soils-and-plant-nutrients
“Soil Facts: Modifying Soil for Plant Growth around Your Home”
https://content.ces.ncsu.edu/modifying-soil-for-plant-growth-around-your-home
“A Gardener’s Guide to Soil Testing”
http://content.ces.ncsu.edu/a-gardeners-guide-to-soil-testing
“Vermicomposting for Households”
https://www.ces.ncsu.edu/vermicomposting-north-carolina/vermicomposting-for-households/