The Best Additive to Lighten Clay Garden Soil

Best Additives for Clay Soil

• Organic soil amendments are the best additives for soil improvement. The best additives for clay soil are fibrous amendments such as wood chips, tree bark or straw. You need to dig the soil additives into your soil and mix them in well if you want to make long-term adjustments to soil quality. Aim to incorporate around 25 percent to 50 percent organic matter to the soil, to improve its overall quality. Adding small amounts of gravel to the soil also improves drainage. Spread between 4 and 5 inches of soil amendment over the top of your clay soil and work it into the soil by hand, or with a rototiller, to a depth of approximately 9 inches; this provides around 50 percent amendment to your original soil.

Mulch

• Mulches give an attractive appearance to gardens, and using wood chips or tree bark eventually adds better quality to clay soils. Once the mulches have decomposed, dig them into the soil to add better aeration, porosity and drainage to your soil.

Worst Amendments to Clay Soil

• It may be tempting to lighten your clay soil with sand; however, you'll find that when wet the soil becomes similar to concrete. Peat is not recommended as an additive for clay soil, because it becomes boggy when wet and soon decays. Although gypsum "clay buster" is recommended for clay soils, it is useful only in alkaline-type soils. Fresh manure is too salty to use as a regular soil additive and needs to be composted. Manure can also import disease to the home garden.

Soil Testing

• Test several areas of garden soil so you get to know the various pH levels of your garden. You can buy simple home pH tests or send soil samples to local laboratories for testing. Once you know whether your soil is neutral, acidic or alkaline, you can decide on the best plants for your garden.