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How to Manage Pests

The UC Guide to Healthy Lawns

Soil amendments

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Organic (material) amendments
Topsoil
Soil pH

Organic (material) amendments

Organic material improves soil structure. Although often not necessary, organic material can be added to sandy soils to increase nutrient and moisture retention. Clay soils can also be amended with organic material to help loosen the soil and provide better aeration and drainage. Compost is the easiest organic material to use. It can be purchased at garden supply stores or can be ordered by the truckload. A rotary tiller works best to incorporate the organic material to your soil. A layer of 1 - 2 inches spread over your site should be tilled to a depth of 3 - 6 inches. Even though some fertilizers are from organic sources, organic amendments are not necessarily fertilizers and should not be substituted for them.

Fertilizers vs. soil amendments

Topsoil

Topsoil may be added to raise the soil level to a minimum depth of 6 to 8 inches. If you choose to add topsoil, do not just lay it on top of the old soil. This may create a layered profile, making it difficult for water to move through or for plant roots to penetrate. The topsoil should be mixed into the existing soil. When adding soil, be sure to add a loamy type of soil that is free of rocks, herbicide residue, weed seeds, propagules such as rhizomes of bermudagrass or nutlets of nutsedge, or other debris.

Soil pH

The ideal soil pH ranges from 5.5 - 7.0. Soils with a pH of 5.5 or lower are too acidic. Lime can be added to raise the soil pH. Soils with a pH of 7.0 or higher are too alkaline and can be modified with elemental sulfur. The professional soil analysis will assist you in determining what kind of amendment you may need, if any.

Photo of adding amendments with a shovel

Statewide IPM Program, Agriculture and Natural Resources, University of California
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