two hands are touching soil in a garden - how to determine the quality of your soil with a soil test
Updated: April 15, 2026

Information provided by a soil test report

A soil test report provided by a laboratory will indicate the levels of nutrients in your soil  as well as other components. Soil acidity level (pH), Phosphorus (P), Potassium (K), Magnesium (Mg), Calcium (Ca), organic matter (OM), and fertilizer and lime recommendations are especially important for maintaining a garden or lawn.

 

a sample soil test report and how to interpret the results of a soil analysis
Sample graphic of a laboratory soil test report, highlighting the various blocks of information. Graphic: Home and Garden Information Center, UME

Download a sample soil report (PDF)

Nutrients

  • An "optimal" or "excessive" or “very high” level means that a nutrient in the soil is more than adequate. Adding more of that nutrient will not improve plant growth.
  • Excessive amounts of nutrients do not harm plants and cannot be physically removed from the soil. There are exceptions, such as when soils are very low in pH and high in aluminum or manganese, making those nutrients available to plants at toxic levels.
  • Phosphorus (P) in particular should not be added if levels are in the "medium" to "optimum" to “high” range. It can get into waterways when soil is moved off-site by erosion. Along with nitrogen, phosphorus feeds the growth of algae in bodies of water like the Chesapeake Bay. When the algae die, it causes a condition called eutrophication - excess nutrients in the water - which leads to low oxygen levels that kill aquatic plants, fish, and other wildlife.

Cation exchange capacity

Cation Exchange Capacity (CEC) measures the capacity of soil to hold and release nutrient ions. Negative charges on clay and organic matter particles attract positively charged ions (cations) like potassium and calcium. Soils with higher percentages of clay and/or organic matter generally have higher CEC. This measurement will vary across Maryland soils. Add organic matter if your soil's CEC is less than 10.

Organic matter

  • Soil organic matter (OM) is made up of living, dead, and decomposing plants, small animals, and microorganisms. Soils high in OM retain more moisture, have a crumbly structure that resists soil compaction, and contain a reservoir of nutrients that are slowly released over time.
  • OM is reported on a percentage-by-weight basis in the lab report. Usually, a sample is weighed in the lab and then ignited to burn off the carbon compounds, leaving only the mineral soil. The sample is reweighed to determine the OM%. Gardeners who add lots of organic matter to their soils may be surprised that the OM content is less than 5%. This is because OM is less dense than mineral soil and the measurement is based on weight, not volume.
  • Healthy soils have a 2% or greater OM content. Regular additions of organic matter will gradually increase the OM level. Where the topsoil is thin and OM is low you may need to add 2 to 4 inches of compost for a few years. Yearly additions of 1 inch of compost can help maintain high productivity in vegetable and flower gardens. It is not uncommon for well-established vegetable gardens to have an OM content above 12%.

Soil pH

  • Soil pH is a measure of how acidic (sour) or basic (sweet) your soil is. The pH scale ranges from 0-14 with 7 as neutral. Numbers less than 7 indicate acidity, while numbers greater than 7 are basic. Soil pH directly affects nutrient availability. For example, phosphorous (P) combines with iron and aluminum when the soil pH is low (below 6.0), and with calcium when the soil pH is high (above 7.3). In both cases, less P is available for plant uptake.
  • Plants have different soil pH preferences. 
    • Vegetables, grasses, and most native and ornamental plants grow best in the 5.5 to 7.0 pH range.
    • Conifers and ericaceous plants (azaleas, rhododendrons, blueberries, and their relatives) prefer acidic soils (pH 4.5 to 5.5).
    • Soil pH values significantly above or below these ranges may result in less vigorous growth or symptoms of nutrient deficiency or toxicity.
  • Most soil test results include soil pH and buffer pH measurement. The soil pH number is the actual pH reading and measures "active" soil acidity. The buffer pH is a measure of the "stored" acidity. The buffer pH is important because it determines how much lime needs to be added to change soil pH. 
    • Soils high in clay and organic matter have a lot of "stored" acidity because these particles have many negatively charged sites that hold cations (positive charges). Hydrogen ions (H+) and aluminum ions (Al3+) are the principal sources of stored acidity. It takes more calcium (lime) to raise the pH of clayey soil than it would for sandy soil. Such soil is more highly buffered, meaning it resists pH changes.
    • Buffer pH is measured by adding a weak 8.0 pH base to low pH soil samples.
    • The lower the buffer pH (the closer it is to the actual soil pH), the more lime is required to raise soil pH.

How to change soil pH

Raising Soil pH

Lime is added to soil to raise the pH.

  • “Garden lime” is made from ground-up rock (calcitic limestone) and provides calcium.
  • “Dolomitic lime” contains calcium and magnesium and is recommended by soil testing labs when soil pH and magnesium levels both need to be increased.
  • Gardeners can choose between powdered, coarsely-ground (granular), or pelletized lime. The finer the particle or mesh size the quicker it will act to raise soil pH.
  • Coarsely-ground and pelletized lime is less likely to clog when applied with a fertilizer spreader to lawns (turfgrass).
  • Hydrated lime (calcium hydroxide) is quick-acting and is not recommended because it can burn garden plants and lawns if used incorrectly.
  • Liming recommendations from soil testing labs are usually given as pounds of ground limestone per 1,000 square feet. Don't spread more than 50 pounds of lime per 1,000 square feet on a lawn in a single application. For example: if the recommended application amount is 85 pounds in total, apply the first 50 pounds now and the remaining 35 pounds roughly six months from now. This gives the lime the time to move down into the soil profile without spiking the pH in the top few inches of soil.
  • Up to 70 pounds of limestone per thousand square feet can be applied in a single application if it is worked into the soil (mixed-in with a rototiller, garden fork, or another tool that blends it with the top few inches of soil).

Lowering Soil pH

Sulfur (S) is added to soil to lower the pH.

  • Sulfur is a highly mobile and soluble nutrient found in the soil as sulfate anions (they have a negative charge). It is difficult to measure accurately and may be omitted from basic soil tests.
  • Soil sulfur deficiencies may be increasing in Maryland as less sulfur is emitted by coal-burning power plants.
  • Elemental sulfur (90% S content), sold as "flowers of sulfur," micro-fine sulfur, and granular sulfur, and iron sulfate (12% S content) are used to lower soil pH. These and other soil-acidifying products are widely available at garden centers and hardware stores.
  • Avoid using aluminum sulfate because aluminum becomes more available with declining pH values and may lead to plant toxicity problems.
  • Use the Clemson University chart for reducing soil pH if the lab does not provide a specific recommendation.

Fertilizer recommendations in a soil test report

Fertilizer for lawns

  • Always follow the University of Maryland lawn fertilization guidelines for nitrogen regardless of the recommendations given in the soil test report. Out-of-state soil testing labs will not necessarily adjust their fertilization recommendations to align with Maryland's lawn fertilizer law.
  • Apply phosphorus (P) to turf only if the levels are low.
  • To convert pounds per acre recommendations to pounds per square feet, do the following math calculation (there are 43,560 square feet in an acre):
    • pounds per acre ÷ 43.56 = pounds per 1,000 square feet
    • pounds per acre ÷ 435.6 = pounds per 100 square feet

Fertilizer for other plants

  • Learn about garden fertilizer basics and find specific fertilization guidance for certain plant groups in the following resources:

Fertilizing Trees & Shrubs Fertilizing Vegetables Fertilizing Fruits

Common questions

How do I select a fertilizer based on the lab’s nutrient recommendations?

Example: Your soil test report recommends applying 2 pounds of nitrogen (N), 3½ pounds of phosphate (P2O5), and 4 pounds of potash (K2O) per 1,000 square feet to your flower garden soil.

Solutions: 

  • Look for a fertilizer with an N-P-K ratio that is close to the amounts of recommended N, P, and K. In this case, the ratio would be 2-3.5-4; or
  • Purchase and apply three separate single-nutrient fertilizers. Examples: nitrate of soda (16-0-0), superphosphate (0-22-0), and muriate of potash (0-0-60).

How do I convert a synthetic (chemical) fertilizer recommendation for an organic fertilizer?

Example: The lab recommendation is to apply 2 pounds of N per 1,000 square feet by applying 4.35 pounds of urea fertilizer (46-0-0). You want to substitute cottonseed meal (6-2-1) for the urea.

Solution #1

Divide the percentage of N in the synthetic fertilizer by the percentage of N in the organic fertilizer, and multiply by 4.35 (the amount of urea).

0.46 ÷ by 0.06 × 4.35 = 33.3 pounds of cottonseed meal.

Solution #2

Calculate the amount of the fertilizer product needed by dividing the pounds of N needed by the percentage of N in the product.

2.0 ÷ 0.06 = 33.3 pounds of cottonseed meal fertilizer per 1,000 square feet.

If your garden is 500 square feet, you would apply half the amount.

Learn more: How to Convert an Inorganic Fertilizer Recommendation to an Organic One

Additional resources

(PDF) Fertilizer Conversions | University of Connecticut

(PDF) Converting Fertilizer Rates from Tons to Teaspoons | Louisiana State University

The USDA National Resources Conservation Service Web Soil Survey

Author: Jon Traunfeld (retired), Director HGIC, Extension Specialist, Fruits, and Vegetables. Revised 2023.

Still have a question? Send it to Ask Extension. Please upload a copy of your soil test results with your question.