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Guidelines for Submitting, Interpreting, and Using Soil Tests

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Providing adequate nutrition to one’s animals is a common goal of livestock producers. Without adequate nutrients and minerals, animals are less productive and return less profit. Many producers understand that one cannot simply “make up for” a protein deficiency by providing animals extra energy, and that dollars are lost by over feeding animals past their nutrient requirements for desired production. We have tools available to help us understand the nutrient requirements of our livestock, help develop a ration (feed), and help determine how much of that ration animals should eat.

However, have you ever considered that these basic principles apply to your forages? To achieve maximum performance of one’s forages, a soil test can be performed to determine the nutrients available in your soil. Then, the requirements of the forage you wish to grow are considered, and fertilizer recommendations are reported from the soil test. Producers can then use test results to apply the correct amount of each nutrient in their specific pasture. More forage growth is seen because your forages have the correct amount of the nutrients they require, and less nutrients (and money) are wasted compared to fertilizing fields with a “best guess” mixture and amount that lacks scientific calculations based off your soil.

How to obtain and interpret a soil test:

1: Take Soil Samples:

Soil can vary in nutrient composition depending on its location in the field. Therefore, it is  important that your soil sample contains soil from each part of the field you wish to fertilize. It is recommended that 15-20 uniform samples of soil are collected from your field. These samples should be 4-6 inches deep and collected in a planned pattern to insure all areas are inspected. Place samples in a bucket, mix well, and place 1 pint in a soil collection box. Soil sample boxes, information sheets, and other supplies for soil testing are available from your county Extension office. When mailing your samples, enclose the filled soil boxes, the information sheet, and a check or money order to cover service charges in a cardboard shipping box and mail to the soil testing lab. More details on sample collection and sample submission can be found on Alabama’s soil test website.

2: Interpreting your Soil Sample Report:

In this article we will focus on the Limestone, Nitrogen(N), Phosphorus(P), and Potassium(K) recommendations from your soil test.

Limestone: Limestone application helps raise the pH of your soil. The pH scale ranges from 0-14 and helps you determine how acidic or basic your soil is. Soil with a pH lower than 7 is considered acidic, soil with a pH of 7 is considered neutral, and soil with a pH higher than 7 is considered basic. In general, if pH drops much below 6, it is time to lime your pasture to raise pH. Apply the amount of Limestone recommended to your pasture. For help with Lime calculations, follow this link.

N, P, K: The amount of each nutrient needed by your pasture is listed in your soil test. Amounts will vary, but the goal of applying fertilizer is to purchase a mixture that best allows these recommendations to be met.  If your soil test recommends 60 pounds of N, 40 pounds of P, and 40 pounds of K, you can custom order this mixture or use a pre-mixed fertilizer to meet your soil’s requirements. For more information on how to calculate the amount of fertilizer needed or the fertilizer mix to use, contact your REA or visit a help page by clicking on the chemical fertilizer calculator help page or the organic fertilizer calculator help page.

3: When to fertilize your pasture:

The key to successful fertilizing is to replace nutrients when they are used by the forages growing in your soil. Different management strategies (grazing vs cutting hay) remove nutrients at different rates and require different fertilizing schedules. Links to fertilizing recommendations for various grasses are given on the ACES website. Click here and select your specific forage to view fertilizer recommendations.

If you have questions regarding submitting and using soil tests, contact myself or other members of the ACES Animal Science and Forages Team.

Sarah Dickinson, M.S.

Regional Extension Agent I

Animal Science & Forages

Alabama Cooperative Extension System

Cell: 256-537-0024

Office: 2560-825-1050

Email:sed0029@auburn.edu

Serving Chambers, Clay, Cleburne, Coosa, Lee, Randolph, Shelby, Talladega, and Tallapoosa Counties