Tests Can Unearth Soil Problems in Your Garden

Before you turn the first shovel of dirt to create your garden, agriculture experts recommend you take a good look at what’s already growing there.

Most soil is not pristine, and problems within are often due to such things as home construction or past gardening.

Frank Himes, an agronomist at Ohio State University, says that during construction, the top layer of soil is usually removed, exposing the subsoil.

Subsoil and other materials excavated for basements are often scattered and leveled by heavy equipment, frequently resulting in infertile and impenetrable material becoming the new topsoil.

Construction also can leave a top layer of soil filled with debris, such as rocks. This debris can interfere with roots and restrict growth.

Previous Gardeners

Activities by previous gardeners could also disrupt your gardening, Himes says. Years of adding peat, sand, lime, acidic materials, fertilizer, pesticide or topsoil can alter the soil significantly.

“The first thing to do is watch what’s growing in the soil and how well it grows,” Himes says. “Stunting, wilting, yellowing or barren areas indicate a problem that could be linked to the soil.”

Getting a soil test is the second thing to do. The test tells you the soil’s fertility and its pH, or alkaline-acidity level.

Soil tests are performed--often free of charge--by local offices of the state’s Cooperative Extension Service. Check your telephone book for the county’s agricultural agent.

A soil test tells you whether the soil is alkaline or acidic. Acidic soil may need lime to buffer it, while alkaline soil may need sulfur or aluminum sulfate to acidify it.

Limestone Can Inhibit

The soil test will tell you how much lime to add but not how much acid-forming material to add. To acidify soil, start by adding small quantities of sulfur or aluminum sulfate, watch how the plants grow, and periodically check the pH.

Limestone, which often can end up on the surface from construction activities in some areas of the country, inhibits the growth of species that prefer acidic soil, such as roses, azaleas, rhododendrons and pin oaks.

Alkaline soils make certain nutrients, such as iron and zinc, unavailable to plants.

Symptoms include yellow leaves and stunted growth, especially on new growth. Foliar fertilizer can correct the problem. The best long-term solution is to add enough acid-forming materials to change the soil’s pH.

The soil test will also tell you how much fertilizer the soil needs, Himes says. Excavated material almost always needs nutrients.