Understanding Your Soil-Test Report

By Wayne Hanna, PhD

If you’re a long-time reader of Whitetail News, then you’ll have read these statements before: Having a qualified soil-testing laboratory test your soil anytime you’re considering buying lime and/or fertilizer is the best tool available to you for ensuring optimum forage growth, and saving money in the process. It can be the difference between having the best food plot you can imagine and total failure.

The first time you see a laboratory soil-test report, though, you may not know exactly how to use the information it provides. That’s especially true of reports that, unlike the Whitetail Institute soil-test report, are structured primarily for commercial farmers. The Whitetail Institute soil-test kit and report are specifically designed for food plotters and can be much easier to read. Even so, it helps to know what information in the report is useful to you, and why. Hopefully, this article will help you easily understand any laboratory soil-test report so that you can quickly take from it the information you need to optimize soil conditions for forage growth. 

The first thing to know is that the information in all laboratory soil test reports can be divided into two main categories, which are often referred to in conversation as “Readings” and “Recommendations.” In short, the Readings tell you what the soil pH, soil-nutrient levels and soil structure of the sampled soil are, based on the laboratory’s analysis; and the Recommendations tell you what to do about the Readings to assure optimum forage growth for the specific forage you’ll be planting or maintaining. 

The most important category from the grower’s perspective are the laboratory’s Recommendations, since they tell you what action you need to take to get certain Readings into optimum range. Even so, you also need to know why the laboratory takes the Readings it does and what they mean if you want to understand why the following statement is true: 

Only a soil test performed by a qualified soil-testing laboratory can assure you that you buy the correct amount of lime, and the exact amount and blend of fertilizer, to assure optimum forage growth and allow you to eliminate wasted lime and fertilizer expenditures! 

 (Soil pH, Soil Fertility, and Soil Structure) 

As previously mentioned, the Readings in a soil-test report are the results of the laboratory’s analysis of your soil, and they’re used by the laboratory to arrive at its Recommendations. But, what is it that the lab is “reading” in the soil, and why? 


Just as humans need to take in food to survive and grow, plants must take nutrients such as nitrogen, phosphorus and potassium from the soil. In each case, two situations must exist: the food (soil nutrients) must be there, and they must be freely available for intake by the plants. 

The first Reading you should look for when you receive your soil-test report is the Soil pH Reading (also sometimes stated as “Water pH”), since it immediately tells you whether or not nutrients in your soil may be inaccessible to your forage plants. Unless soil pH is within the optimum range for the forage being planted or maintained, the forage plants will not be able to freely uptake nutrients from the soil. That makes the soil pH Reading (and when soil pH is low then also the attendant lime Recommendation we’ll discuss later) the most important information on your soil-test report. Put simply, soil pH is a measurement of the alkalinity or acidity of soil, and that measurement is represented by a number, most commonly from about 4 to about 8. A number from 6.5 – 7.5 defines “neutral” soil pH. Numbers below that range indicate “acidic” soil, and higher numbers define soil that is “alkaline”. Most fallow soils are acidic. And since we often find fallow sites covered with grass and other weeds, it stands to reason that many naturally occurring grasses and weeds can freely uptake nutrients from soils within a fairly wide soil pH range, including neutral and acidic soils. And that’s the reason for the common misconception that a site will sustain forage plantings well just because grass and other weeds flourish there. Most high-quality forage plantings can freely uptake soil nutrients only in soils with neutral soil pH — a much narrower range. Why is that important to understand? Because plants growing in the site cannot freely uptake nutrients from the soil unless soil pH is within the range in which they can do so. Still not convinced? Okay, let’s put it in terms your wallet can understand. High-quality forages planted in a site with a soil pH of 5.0 can only access about 46 percent of the nutrients in the soil. That means if you spend $100 on fertilizer for the plants in that plot, you just wasted $54! 

(Soil-Nutrient Levels)

Most laboratory soil-test reports list soil nutrient Readings in parts per million (ppm). “Optimum level” doesn’t mean the same thing for all crops; some require higher levels of specific nutrients than others, so if your soil test report only lists these levels in ppm, then you’ll need to find out what the optimum level of that specific nutrient is for the specific forage you’ll be planting or maintaining. 

Some reports such as the Whitetail Institute’s soil-test report, though, also provide this information in a format that’s much easier for food-plotters to understand. For example, the Whitetail Institute report’s Readings are also expressed in lbs./acre, which is more familiar to many folks, and even provides an easy-to-read bar graph that tells you in an instant whether the level of a particular nutrient in your soil is low, sufficient for the coming year, high, or even too high. 

Specific nutrient levels specified in most soil-test Readings include nitrogen, phosphorous, potassium, calcium, magnesium, boron, copper, iron, manganese, sulfer and zinc. 

Nitrogen, Phosphorous and Potassium. The most important nutrients by far to most food plotters are nitrogen (N), phosphorous (P) and potassium (K). Focus on these. They’re the “Big Three”. 

Calcium, magnesium, boron, copper, iron, manganese, sulfur and zinc. Other nutrient Readings you may find on your soil-test report may include calcium, magnesium, boron, copper, iron, manganese, sulfur and zinc. When the crop being planted is intended as a food plot to attract and hold deer rather than for harvest, these Readings can be largely ignored. While that’s not true in all cases, it’s true in such a majority that the role of these nutrients and the effect of their levels won’t be covered within the scope of this article. Also, as previously mentioned, calcium and/or magnesium, if low, will be addressed if the vastly more common dolomitic type of lime is used to raise soil pH. 


So far, we’ve covered why soil pH and soil nutrient levels must be at (or brought up to) certain levels for the forage plants to have access to all the nutrient levels they need. 

Why, then, isn’t there a chart out there that says exactly how many pounds of lime should be added in all cases to raise the soil pH of all soils with the same starting soil pH to the same target soil pH? The answer reveals why when it comes to having your soil tested, a laboratory soil test is the only way to go; and it will make sense to anyone who has ever noticed that dark, bottomland soil doesn’t look like the soil in a sandy ridgetop: all soils aren’t the same. And just as they don’t look the same, not all soil types hold lime activity and nutrients as long or as well as others. For example, “heavy” soils such as clays or soils with lots of organic matter tend to hold lime activity and nutrients better than soils that are “lighter” or have a higher sand content. That’s why only a laboratory soil test can precisely tell you exactly how much lime and/or fertilizer you need. If the lab’s nutrient and soil pH Readings are below optimum, then the lab will consider what levels of nutrients are already in the soil, apply its findings as to how well (or poorly) your soil can hold lime and fertilizer activity, and develop its Recommendations accordingly — based on the unique physical characteristics of the soil in your sample. 

Since the laboratory’s soil structure Readings are simply sub-calculations the laboratory used in arriving at its final Recommendations, they are things you can ignore as a practical matter. If you’re still interested, though, here’s what they mean: 

Buffer pH. On some soil test reports, you may see “Buffer pH” listed. Buffer pH really tells you nothing. It’s simply the result of a test done at the laboratory to help it form its final Recommendations for how much lime to be added to soils with low soil pH. A liming material called a buffer solution is added to the soil sample, and the increase in soil pH is then measured and used by the laboratory in reaching its final lime Recommendation. A big jump in soil pH suggests that the soil pH of the sample is easily changed, and vice versa if the change is small. The laboratory then uses this calculation in reaching its final lime Recommendation. 

Organic Matter and CEC: The “Organic Matter” Reading indicates the amount of organic matter in your soil. “CEC” (Cation Exchange Capacity) is a measurement of the soil’s ability to release positively charged nutrients, or “Cations.” Together, Organic Matter and CEC tell the laboratory how well (or poorly) the soil can hold nutrients. The lab uses the Organic Matter and CEC Readings together as part of its final calculations for its Recommendations. 

 (Lime and Fertilizer) 

Recommendations are the most important things on a laboratory soil test report, since they tell you what action you need to take (what you need to add to the soil) to bring it into optimum condition if planting, or to maintain optimum condition if maintaining an established forage stand. 


If your soil pH Reading is below optimum for the forage being planted or maintained, then the soil-test report will also make a Recommendation as to how much lime to add to the soil to raise it. This is one of — if not the most — critical Recommendations your soil-test report will make. That’s because high-quality forages that grow best in soils with a neutral soil pH won’t be able to freely uptake soil nutrients if soil pH is low, so lime should be added to raise soil pH in such cases, if possible several months in advance of planting. 

Most laboratory soil-test reports will provide Recommendations for the amount of lime that needs to be added when the soil pH reading is low. Don’t be surprised if you see the lime recommendation expressed in tons per acre. (The good news is that lime is relatively inexpensive, especially when purchased in bulk.) The reason it takes so much lime to raise soil pH is that lime does its work by acting in particle to particle contact with the soil. In other words, a particle of lime needs to touch a particle of dirt to neutralize its pH. The fact that tons of lime are usually required makes more sense when you understand that and consider how many particles of dirt are in the top few inches of a one-acre seedbed. 

The recommended liming material to raise soil pH is crushed limestone rock. There are two types of limestone rock that are mined and then crushed for use in raising soil pH: dolomitic and calcitic. How quickly they can raise soil pH depends on whether it’s dolomitic or calcitic limestone, how finely it’s crushed, and how thoroughly it is incorporated into the soil. 

While both dolomitic and calcitic limestone are used as liming materials to raise soil pH, dolomitic is far more common. In fact, if you buy lime for your food plot, chances are extremely high that it will be dolomitic limestone. In most cases, dolomitic is preferable for several reasons: (A) calcitic acts more quickly, but it carries an attendant risk of over-liming, which is not presented with dolomitic; (B) dolomitic already has magnesium in it; and (C) dolomotic’s liming effect lasts longer. Whether the lime is dolomitic or calcitic, it can’t work overnight. That’s why for best results, you should try to plan ahead and, if possible, incorporate lime at least several months in advance of planting. 


Most soils already have some nutrients in them, although most fallow soils usually don’t have sufficient levels for high-quality forage plants to really thrive, so we add fertilizer to the seedbed to bring those levels up. 

As we mentioned earlier, the “Big Three” nutrients addressed with blended fertilizers are nitrogen, phosphorous and potassium. When you review the fertilizer Recommendations in your soil-test report, though, you may notice that those terms don’t appear. Instead, you’ll see similar sounding titles such as “nitrate” and “phosphate.” Don’t let that confuse you. For our purposes, just remember that nutrient Readings are shown by the names of their natural forms, and the Recommendations are for those same elements, but in compounds used in fertilizers to make those elements available to plants. Here’s how you’ll see the Big Three listed: 

Element                                                       Compound (Fertilizer Form) 
Nitrogen (N)                                                 Nitrate 
Phosphorous (P)                                          Phosphate 
Potassium (K)                                      Potash* 
* The commonly used name for potassium-compound fertilizers. 

Calculating fertilizer rates. Most, if not all, laboratory soil-test reports make fertilizer Recommendations in two formats: pounds per acre, and for smaller plots, pounds per 1,000 square feet. 

Blended fertilizers in bags are labeled with a series of three numbers separated by dashes, for example 13-13-13 and 6-24-24. In order from left to right, those numbers tell you the percentage of N, P and K in the package. 

The Whitetail Institute soil-test report provides a chart (Table 2) that suggests different combinations and amounts of readily available bagged fertilizers common to many areas that will satisfy the nutrient Recommendations in the report. Each block may suggest one, two or three different fertilizers. It’s important to understand that each block (and everything in it) is a single option, and that all the other blocks (and everything in them) are alternatives. 

For example, take a look at Table 2 in this article. In the first block (highlighted in red), you can see that 10-10-10, 0-20-20 and 0-46-0 are recommended. If you can find all three of these fertilizer blends in your area, then apply all three, each in the amount (lbs./ac or lbs./1,000 sq. feet) as recommended in Table 2. If you aren’t able to locate all three of the fertilizers recommended in the first block, then go to the second block (highlighted in blue), which recommends 15-15-15, 0-20-20 and 0-46-0. Not all soil-test reports have more than one recommendation. If you can’t locate fertilizers in your area that satisfy at least one of the Table 2 blocks, then call the Whitetail Institute for additional advice. 

 Preparing And Sending the Soil Sample to the Laboratory 

Most, if not all, laboratory soil-test kits come with at least two items: a submission form, which asks you for specific information the lab will need to process the sample and prepare a precise report for you, and a container for sending in the soil you want to have tested. 

Submission Form. Most, if not all, submission forms ask for the same basic information, such as your name and address. Be sure to write legibly so the lab can correctly label the report for mailing. 

Two more things: it’s very important to tell the lab (A) whether you will be planting or maintaining a forage in the site, and (B) what that forage is. The reason is that soil pH and fertilizer requirements differ among plant types, and among those, some differ with regard to planting and maintenance. The Whitetail Institute soil-test kit also makes this step very easy. All you have to do is check a block beside either “Establishing New Field” or “Maintaining Existing Field,” and another block beside the name of the Whitetail Institute forage product you’ve chosen. Or, you can choose “other” if you have decided to plant something other than a Whitetail Institute forage product. If you haven’t completely decided on what forage you’ll be planting, you can even check up to two forage-product blocks, and the lab will provide Recommendations for both at no additional charge. 

Preparing the Soil Sample: Keep in mind that you’ll be sending in a relatively small amount of soil (about a pint), and that sample must be representative of all the soil in the top few inches of the entire seedbed. If you’re planning on plowing the seedbed with a moldboard plow, which inverts dirt in a column, try to do your plowing before you take your samples if possible. That way, you’ll be testing the soil in which the plants will actually be growing. 

Take samples one to six inches deep in 10 to 20 locations within the seedbed after scraping away plant residue from each sample location. Mix all the samples together thoroughly in a clean, plastic container. If the soil is wet, then allow it to air dry to a workable condition before packaging it. Then, put the representative sample into the soil-sample container provided in the kit. 

Sending the sample to the laboratory. Be sure to package the soil-sample container and the submission form together. Do not mail them separately. If you have more than one sample, it can also be a good idea to seal each sample container and its accompanying submission form in a separate shipping envelope, and then put all the sealed envelopes into one box to ship. That way, you can be sure all the samples arrived at the same time, and you can track the shipment. 

If you need assistance interpreting your Whitetail Institute soil-test report, or a soil-test report from any other laboratory, call the Whitetail Institute’s in-house consultants at (800) 688-3030. The call and advice are free.