Mar 24, 2007 2 min read

Springtime is a good time to add soil amendments that will improve the soil structure, texture and its plant support mission. Clay soils offer some special challenges, so this week we will focus on improving them.

Clay soils have several disadvantages:

First, they tend to compact easily. Compacted soils have a hard, dense layer on the surface that prevents water, air, and fertilizers from moving downward.

Compaction reduces the air spaces in the soil.

Without enough oxygen, plants develop shallow root systems that are more prone to drought stress.

There is just one practical way to improve clay soils.

You need to work in organic matter.

Commonly available sources include peat moss, rotted animal manure, and various kinds of compost.

Leaf, wood, or grass clipping composts all work well.

Dig organic matter into the soil each year, either in early spring or fall.

Work organic matter into a six- to ten-inch depth, and use about one bushel of loose peat moss, rotted animal manure, or compost for every 20 square feet of garden.

Add organic matter to annual flower and vegetable gardens every year.

Many gardeners neglect this important step.

Organic matter is used up over time, and you need to replace it regularly.

When you plant trees and shrubs, adding organic matter to the planting hole is usually not recommended because changing the soil structure drastically inhibits roots from growing out of the hole.

It’s best to plant trees and shrubs in existing soil, even if it is high in clay content.

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Cathy Brady and Don Fretts are educators with the Penn State Cooperative Extension, an educational network that gives people access to the resources and expertise of Penn State University.

Penn State Cooperative Extension is funded by the U.S. Department of Agriculture and state and county governments. Local extension educators and volunteers can be reached at fayettext@psu.edu or by phone at 724-438-0111.

For more information, check the state’s extension website at www.extension.psu.edu.