How to Make Clay Soil Better

Gardeners generally categorize soil into three types-sandy, loam and clay-with clay being viewed as the most challenging. Although it's often rich in nutrients, clay drains poorly and compacts easily, making it a poor medium for plant root development (especially for root crops such as carrots). With specific soil amendments, gardeners can condition their clay soil and improve its drainage and permeability to better support the plants they wish to grow.

First, breakup the soil. Use a spade or rotary tiller to break up the top 8 to 10 inches of your garden's clay soil. This is the area in which most plants' roots grow, according to North Carolina State University.

After breaking up the dirt, spread 1.5 cubic yards of organic soil amendment for every 500 square feet of gardening surface. Because clay soil has high water retention but low permeability, use an amendment that has high permeability but low moisture retention. Colorado State University recommends using shredded bark or wood chips. Mix the soil amendments into the top of the soil surface. The clay soil's draining characteristics will be immediately improved. As the organic material decomposes, the soil's condition will be further enhanced.

Protect the soil after you've amended the d irt. Spread a 2 to 3 inch layer of mulch over the amended soil. This further helps to condition the soil and also shields it from compaction when you walk in the area. Wait for 3 to 4 months to allow the organic material to break down before resuming use of the soil.

In a word of closing, never use sand. Contrary to popular opinion, adding sand to clay soil is a terrible idea. The sand only helps make the clay compact more quickly, according to North Carolina University, which likens it to making bricks.

References:

"The Vegetable Gardener's Bible, 10th ed."; Edward Smith; 2009

Colorado State University: Choosing a Soil Amendment

North Carolina State University: Amending Clay Soils