How to Read a Lawn Soil Test: A Simple Guide for Homeowners

A lawn soil test can look complicated. There are numbers, charts, nutrient names and calculations that most homeowners rarely encounter.

The good news is that you do not need to understand every number on the report. For most lawns, there are four main things to look at:

• Soil pH
• Whether nutrients are low, adequate or high
• Organic matter
• What the laboratory recommends adding

What Does a Soil Test Tell You?

A soil test helps us understand what is happening in the soil where the grass is growing. It can tell us whether important nutrients are available, whether the soil pH is in a reasonable range and whether changes to the fertility program may help the lawn.

Just as importantly, a soil test can tell us when nutrients are probably not the reason a lawn is struggling. That can help us focus on other possible problems such as watering, mowing, sunlight, insects, disease or soil conditions.

How to Identify the Important Information on a Soil Test Report

At first glance, there is a lot happening on a soil test report. What we want to find is…

• Soil pH
• Whether nutrients are low, adequate or high
• Organic matter
• Laboratory recommendations.

There is typically other information on the soil test. This information is helpful in some situations, but typically not used in the analysis of a soil test.

• Where the sample was taken, when it was received and who analyzed it.
• The actual soil test results.
• Calculations on the results for deeper investigations. These numbers can provide useful information to an agronomist when diagnosing more unusual soil problems. Most homeowners do not need to understand or interpret these calculations.
• Further notes about recommendations.

Let’s talk about the key information on the soil test using a real world soil test report…

Step 1: What is the soil pH?

One of the first numbers on most soil tests is soil pH. Soil pH affects how easily grass can access nutrients that are already present in the soil.

The pH in our example is 5.7. That is somewhat more acidic than we commonly see, but grass can still grow well at this level. In this case, we would recommend lime to gradually increase the pH.

We look at soil pH as one part of the overall picture rather than assuming that a slightly high or low pH is automatically causing a lawn problem.

Step 2: Are Your Lawn Nutrients Low, Adequate or High?

This is where the colored rating chart becomes especially useful. Instead of focusing on every individual number, we can group the nutrients by what the test is telling us into 3 groups

• Adequate Nutrients – There are enough of these nutrients to grow a healthy lawn.
• High Nutrients – There are more than enough nutrients to grow a healthy lawn. Depending on the nutrient it is possible that high levels are detrimental to growth.
• Low Nutrients – Supplemental fertility of these nutrients is helpful to growing a healthy lawn.

In this example…

• Adequate nutrient levels = phosphorous, calcium, copper, manganese and zinc. Adding more of these nutrients is not required for healthy lawn growth.
• High nutrient levels = magnesium and iron. In this case, too much is not a problem, but more does not need to be added.
• Low nutrient levels = Sulfur, potassium and boron. In this case, adding more of these nutrients could help the lawn grow healthier.

Step 3: What Does Organic Matter Tell You?

This soil contains 5 percent organic matter. Organic matter helps the soil hold moisture and nutrients and supports biological activity in the soil.

For a home lawn, 5 percent is a good result. In this example, low organic matter would not be something we would identify as a likely reason the lawn is struggling.

Step 4: What is the laboratory recommendation?

This is the most important part of interpreting the report.

Overall, this soil test looks pretty good. There is no major nutrient deficiency that would immediately explain a lawn performing poorly. Most nutrients are already available in adequate amounts.

There are still some opportunities to improve the fertility program. The laboratory suggests additional potassium and sulfur, along with a very small amount of boron. The soil is also somewhat acidic, so lime could gradually move the pH higher.

At the same time, we can see several things we probably do not need to add. Magnesium, iron and several other nutrients are already readily available.

If this lawn were struggling, this soil test would tell us to start looking beyond fertility.

We would want to investigate things such as watering, mowing practices, sunlight, soil conditions, insects, disease and the types of grass growing in the lawn.

Sometimes the most valuable result of a soil test is learning what isn’t causing the problem.

What About Nitrogen?

You may notice that nitrate nitrogen does not have a result on this report. That does not mean the soil contains no nitrogen.

Nitrogen behaves differently from many of the other nutrients in the soil. Its availability changes throughout the growing season, so a single soil test number is often less useful for determining how much nitrogen a lawn needs for the entire year.

Instead, nitrogen recommendations are generally based on the type of grass, growing conditions and how the lawn is being maintained.

For this bluegrass lawn, the laboratory recommends about 3 pounds of nitrogen per 1,000 square feet annually.

What Can’t a Soil Test Tell You?

A soil test is a great tool, but it does not diagnose every lawn problem.

It cannot tell us whether a lawn is receiving enough water or whether it is being mowed too short.

It does not tell us whether a lawn has an insect or disease problem.

It cannot fully evaluate shade, drainage, soil compaction or whether the grass varieties are well suited to the location.

That is why a soil test is one part of diagnosing a lawn rather than the entire diagnosis.

Does Every Lawn Need a Soil Test?

If soil tests provide this much information, why doesn’t bioLawn recommend one for every lawn? The reason comes down to the amount of local information we have already evaluated.

bioLawn has evaluated thousands of soil tests throughout the Twin Cities and surrounding communities. That has given our agronomy team a strong understanding of the nutrient levels commonly found in the soils throughout the areas we serve.

We have used that information to design our fertility treatments around the needs we already exist in the neighborhoods we serve. Being a local company allows us to tailor our fertility treatments to what neighborhoods need.

Because of that, most lawns do not need an individual soil test to perform well.

Soil testing becomes especially valuable when a lawn is not responding the way we expect and the reason is unclear. In those situations, a soil test helps us answer an important question: Is there something missing from the soil, or should we be looking somewhere else?

Many times, the soil test confirms that nutrient levels are already adequate. That is still valuable information. By ruling out a major fertility problem, we can focus our attention on what is actually limiting the lawn.

Ultimately, that is what a soil test does best. It gives us better information so we can make better decisions about what a lawn needs and what it does not need.