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Using the WVU Soil Testing Report

A copy of WVU's Soil Test Form sits on the ground amid plants and containers.

The WVU Soil Testing Lab report is divided into four sections – submission information, laboratory test results, fertilizer recommendations and recommendation notes.

The submission information in the top section contains the name, address, county, phone number and email address of the customer submitting the soil sample. These are needed for identifying and communicating with the customer. An email address enables us to report directly to customers, providing a faster return. If no email address is provided, a hard copy is sent by conventional mail to the customer, which may take extra time. Phone numbers are only used to contact customers if there is a problem with their submission.

When possible, use the fillable digital submission form (PDF) to reduce handwriting errors. For customers who are not able to use a computer at home, this service is available at their local WVU Extension office.

This section provides the customer sample ID for where the sample was taken. The customer sample ID is the field name or number used by the customer for their records. Maintaining the same sample ID for future samples allows the customer to follow and evaluate management impact on soil test values. Lab ID is used by the laboratory to lookup a specific soil sample submission.

Field size in acres or square feet determines if recommendations are provided in pounds per acre or ounces per 100 square feet. Soil series and the crop code are used to determine fertilizer recommendations. For home gardens, high tunnel and commercial vegetable production soil series is not used in determining recommendations, so it is not needed. If you have questions on any of these items, contact your local WVU Extension agent for assistance before sending in your sample.

Laboratory Test Results

Laboratory results reported include soil pH, content of elemental phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in parts per million (ppm), and calculated P saturation (Psat). Soil organic matter (SOM) and electrical conductivity (EC) also are available when purchased by the customer.

These values are based on Mehlich-3 extraction, read with ICP technology. These values are used with the crop code and expected yield to generate the fertilizer recommendations. If the same soil sample were sent to a different lab, reported values could differ due to different laboratory methods or reporting results as pounds of oxide or element per acre.

Soil fertility is also reported as low, medium or optimum relative sufficiency. Bar graphs for P, K, Ca and Mg are provided to show the relative sufficiency with 100 indicating the low end of the optimum range. Soils testing in the optimum range should have an adequate supply of that nutrient for the crop to achieve expected yield without adding fertilizer containing that nutrient. Soils testing in the medium range need a small amount of additional fertilizer nutrient to achieve expected yield. Soils testing in the low range need the indicated larger amount of fertilizer nutrient to achieve expected yield.

The Psat index measures risk for soils testing excessively high in phosphorus, contributing it to surface water and causing pollution. A low P saturation (less than or equal to 15) means that there is low risk for losses to the environment.

The soil organic matter report is the measure of organic matter, which is beneficial for moisture and nutrient availability for plant growth.

The electrical conductivity report measures the salt content in the soil due to excessive fertilization or lack of adequate irrigation in high tunnels. High EC reduces water uptake and can reduce crop yields. When the EC value (1:1, soil:water dS/m) is greater than 0.7, it is recommended to leach the excess salts out of the soil using rainfall or increased irrigation.

Fertilizer Recommendations

Agronomic crop fertilizer recommendations are based on the expected yield for the specified crop when grown on the indicated soil type. When the predominant soil series is not provided, a yield class two soil is used as the default. To upgrade the recommendation, the local WVU Extension agent can help identify the predominant soil series and generate an updated recommendation.

Fertilizer recommendations are reported as N, P 2O 5, and K 2O fertilizer nutrients required to achieve expected yields. These recommendations are reported as pounds per acre or ounces per 100 square feet, depending on the area units provided in the submission. If there is a change in the crop being planted after a soil sample is submitted, the local WVU Extension agent can update the submission with a new crop code and print out a report with recommendations for the new crop.

Two levels of fertilizer recommendations are given – crop sufficiency and build to optimum. The crop sufficiency level is the minimal level of fertilizer that should be used each year to achieve the expected yield. This is the lowest cost fertilizer recommendation and is recommended for land rented on an annual lease. The build to optimum is a higher fertilization rate that will build soil fertility into the optimum soil test range over time. When the soil test is in the optimum range, soil fertility can be maintained to a large extent on livestock farms by cycling nutrients in the crops through good manure management. The optimum range also provides nutrient reserves to reduce the need for phosphorus and potassium applications in years when fertilizers prices are excessively high.

Lime recommendations are reported as 100% effective neutralizing value (ENV) agricultural lime. To calculate the tons of lime product needed to equal 1 ton of ENV lime, use the WVU Extension Value of Agricultural Limestone worksheet (Excel XLS Format).

The lime recommendation is for raising the measured soil pH into the pH range for the indicated crop. For alfalfa, the lime recommendation is for a pH of 6.6 with a maximum application rate of 3 tons ENV lime at any one time. For other agronomic crops, when soil pH drops below 6.0, 2 tons ENV lime are recommended. For blueberries and brambles, which prefer a pH below 6.0, no lime is recommended.

For plants that prefer acid soils, such as blueberries, brambles, shrubs, flowering plants and Christmas trees, use the soil test pH and other information to determine if aluminum sulfate or sulfur should be used to lower soil pH.

Magnesium (Mg) recommendations are based on optimum health for livestock consuming forage and humans consuming leafy green vegetable crops. Grain crops can tolerate magnesium levels in the medium range, but when grown in rotation with forage crops, the rotation system benefits from magnesium in the optimum range. Dolomitic lime is the lowest cost source for increasing soil test magnesium. High calcium lime sometimes contains adequate magnesium to move soil test levels into the optimum range. Sources of magnesium that should be considered as magnesium fertilizer include:

  • Dolomitic agricultural lime
  • High calcium agricultural lime that contains measured magnesium content
  • Pelletize dolomitic lime in small amounts
  • KMgSO 4 fertilizer when available
  • Magnesium oxide mixed in blended fertilizers
  • MgSO4 (Epsom salt), a preferred source in home gardens

For soils testing below optimum in magnesium, several notes are provided for increasing soil test magnesium relative to measured soil pH.

Recommendation Notes

Detailed recommendation notes specific to the crop are provided on the reverse side of the soil test report. These provide valuable management suggestions for the crop.

Modifying Recommendations

To identify the predominant soil series in a field, use the University of California Davis SoilWeb or the USDA NRCS Web Soil Survey.

To calculate a blended fertilizer recommendation, use the WVU Extension Blended Fertilizer Calculator, or the University of Georgia Extension Fertilizer Calculator.

To change fertilizer nutrient recommendations from pounds per acre to ounces per 100 square feet, multiply pounds per acre by 0.0367 (100 pounds per acre x 0.0367 = 3.67 ounces per 100 square feet).

When a recommendation is in ounces per 100 square feet and it is wanted in terms of ounces per feet of row length, divide 100 square feet by the row spacing to get the linear feet of row that the recommendation should be applied to (100 square feet/3 feet of row spacing = 33.3 feet of row length; 100 square feet/2 feet of row spacing = 50 feet of row length). For raised beds, the same applies by substituting bed width for row spacing with the results equaling bed length.

Fertilizer recommendations for agronomic crops are based on expected yield for the indicated crop on the predominant soil or the default yield class when no soil type is provided. However, the manager may know that yields on their farm differ from these estimates and need to modify fertilizer recommendations.

Hay crop fertilizer recommendations are based on a three to four cut hay system with nitrogen provided by legumes or by applying 50 to 60 pounds N per acre prior to each hay cut. When fewer than three hay cuts are made, the fertilization rate for P 2O 5 and K 2O can be reduced. When legumes are not used as the source of N, 50 to 60 pounds N per acre should be applied for each hay crop. The first hay crop produces about half of the annual yield with the remaining yield spread over the other harvests.

For hay yields lower than the expected yield, reduce the recommended P 2O 5 and K 2O fertilization rates proportional to the reduced yield. For example, the expected yield is 4 tons per acre, but the farmer plans to take one cut of hay and graze all the aftermath growth during the summer and fall. The first cut hay crop produces about one-half the expected yield. Therefore, the P 2O 5 and K 2O recommendations can be cut in half by dividing by two. When soil test levels for phosphorus and potassium are in the optimum range, no additional P 2O 5 or K 2O fertilizer is needed for the portion of the crop that is grazed since these nutrients are recycled to the soil by the grazing livestock.

For corn crops under excellent management, the achieved yield on the best soils may be higher than the expected yield used in the recommendation. In such cases, the fertilization rates for N, P 2O 5 and K 2O should be increased in proportion to the historically achieved yield. For example, the expected yield is 120 bushels of corn, but the achieved yield has averaged 160 bushels per acre or 33 percent higher (160/120 = 1.33) over the last three years. Therefore, the recommended N, P 2O 5 and  K 2O fertilizer rates should be multiplied by 1.33 to achieve the needs of this higher producing crop.

Ed Rayburn, Retired WVU Extension Specialist – Forages and Agronomy
Tom Basden, Retired WVU Extension Specialist – Nutrient Management

Last Reviewed: July 2020