How to Amend Clay Soil

One would think that to fix the balance of clay one should add sand. Well, not exactly. The reason is that yes, it will work, but its not a practical solution. Here’s why. Adobe, which bricks are made from, is clay and sand, period. Adding the wrong amount of sand (too little) will turn your clay soil into adobe! To add enough sand to a 20’x50’ garden area it will take 3-5 tons of sand! An expensive and heavy prospect.

Often gypsum is recommended by well-meaning nursery workers. Gypsum will only work if your soil is on the alkaline side. It is best to have your soil tested at your local County Agricultural Extension Office before trying gypsum.

Interestingly enough, the best and only way to amend any soil, clay or otherwise is by adding organic matter. Organic matter creates humus which is food for earthworms and other soil dwelling microbes. These soil dwelling creatures help digest the humus and in so doing create little pockets of air (which plants and little soil dwellers need) and tunnels (worms) which water and nutrients can flow through. The little particles of matter also help separate and open up small densely packed clay molecules.

The ideal organic matter for clay is Redwood Soil Conditioner. Why? Because redwood takes 3-5 years to fully decompose in the ground, during this time it is feeding the soil microbes and creating the air space. Homemade composts work equally well. Just put 2-3" layer on the surface and lightly work into the soil before planting. Remember to add some organic matter every year to keep the worms happy and sticking around.