Putting Your Soil to the Test

A simple test that can help your lawn make the grade is a soil test. At the beginning of spring, many homeowners start a lawn from scratch or renovate an existing lawn. The first step for either activity is to perform a soil test to determine the physical and chemical makeup of the soil, allowing homeowners to appropriately modify their lawn care practices, depending on the results.

Who Needs One, Who Doesn't

How do homeowners know if they need to conduct a soil test? If an existing lawn is on a regular lawn care regimen and shows relatively few problems, a soil test should not be a top priority. On the other hand, if an existing lawn has been experiencing signs of disease or reoccurring problems, a soil test is an appropriate action to take in spring to tackle lawn care in a more informed manner throughout the season. In addition, for homeowners starting a lawn from scratch, a soil test is a necessary first step to the Yard Doctor's 10-step procedure.

Two Test Types

The most common test used when starting a lawn from scratch or renovating a problematic lawn is called a basic soil test. It will inform the homeowner of the soil pH and the nutrient levels such as phosphorous, potassium, calcium and magnesium. In addition, test results will provide a cation exchange capacity (CEC), which indicates the soil's ability to retain nutrients.

Sometimes, a second test called a physical soil test is important (this is in addition to a basic soil test) for homeowners who suspect different soil types in their lawn or for those who plan to amend or import another soil into their lawn. Results of a physical soil test provide information about the granular sizes, or texture, of soil types and report percentages of sand, silt and clay-sized particles. Incompatible soil types may cause lawn-related problems such as poor drainage and increased susceptibility to diseases. A common problem that results from construction or sod establishment is soil layering (see image). Soils of finer texture are layered over a soil of coarser texture, which disrupts water flow and makes the soil too wet. In contrast, compatible soil types that are mixed appropriately will make soil additions or amendments quite easy and will allow for a healthier lawn in the future.

Following Test Instructions

When it comes to conducting a soil test, many homeowners do not know how to get started. Take the following steps when collecting samples:

• Start at the County Extension Office or a local garden center to obtain a soil test container or a soil test kit. These usually run about $10-$15.
• Identify how many samples to collect and where in the lawn to collect these different samples. The idea behind a soil test is to evaluate the characteristics of the soil. For each suspected different area of the yard, collect 10-20 sub-samples from each. Enough sub-samples prevent erroneous conclusions due to one volatile sub-sample (for instance, a sample from an area where a pet recently visited).
• One example of an area where samples may differ include forested vs. sunny areas. In addition, the soil near a home's foundation differs from other areas of the yard because it often comes from digging the basement foundation. This soil contains fewer nutrients and does not promote healthy grass establishment. A soil test will help solve these problem areas.
• Once the yard is divided into the desired number of segments, collect 20 soil sub-samples from each one. To do so, dig soil out with a small shovel or spade. The sub-samples need to be four to six inches in depth and about the size of a couple of fingers in volume.
• For each separate lawn segment, mix the 20 sub-samples and place the resulting soil sample on a newspaper to air dry. Once dried, thoroughly mix the sample further, and fill up the soil test container. Do this for each lawn segment.
• Take all the containers to the soil testing facility to be tested.

Test Timing

When establishing or renovating a lawn, conduct a soil test about a month before starting the project. This will give the soil testing facility time to complete their work, and will allow the homeowner time to implement the facility's suggestions based on the results. Testing more than a month prior to the work will most likely yield valid results, but conducting the test too early will not show results representative of the soil at the time the renovation is performed.

Reading the Results

On most chemical soil test result reports, homeowners must first look at soil pH levels. The soil should be at a pH level between 6.0 and 7.5. If the pH is below that range, it may be necessary to raise the soil's pH with lime applications. Next, look at the CEC. If the CEC is below five, homeowners may want to add more fertilizer to their soil when establishing a lawn. Other key results to review are the potassium and phosphorous levels.

Although the soil test results may recommend adding nitrogen to the soil, a specific soil nitrogen level may not be reported in the standard soil test. Soil nitrogen levels are considered so dynamic, or readily changeable, that reporting them with any delays could lead to wrong conclusions and applications. In other words, a soil test could have adequate nitrogen levels at one point, but these levels might dramatically alter after a three-inch rainstorm.

There will likely be fertilizer application rate suggestions to follow from the soil testing facility, but ask questions if the results seem confusing.

Score Winning Marks in Lawn Care

A simple soil test is an important step to starting a lawn from scratch or renovating an existing lawn. When the proper soil modifications are made, the results will yield a lawn that can be enjoyed by all.