The Soil Analysis Report

The soil analysis report should come in the mail about 10 days after submitting the soil sample to be tested. For faster results, some labs are set up for viewing reports online. Check with the lab or extension office to see if they offer that service. Click here for easy instructions on how to collect a soil sample.

Understanding the soil analysis report can be difficult. The testing labs use soil chemistry and turf industry terminology to describe the results without any explanation as to what the terms mean.

Careful examination of this page should help you in interpreting the results seen on a typical soil analysis report as well as provide you with a number of helpful lawn care tips. Beautiful lawns are not created accident, but by understanding the needs of your grass.

A look at what is on the soil analysis report

Cation Exchange Capacity (CEC)

The CEC is one of the first results you see on the soil analysis report. It can be complicated and probably the hardest to understand, but is an important part of soil science. It is included in the soil analysis, because it is necessary for professional turf managers, but is also very useful for homeowners as well. A very basic explanation is provided below, but a complete explanation is beyond the scope of this site. For more detailed information, you can click on this Clemson University CEC site.

Soil analysis results denoting low CEC soils, such as sandy soil, will need the fertilization adjusted to deliver less fertilizer per application, but performed more times per year. Sandy soils don’t have as many negative charges to hold nutrients, so it will need to be approached a little differently. The total amount of fertilizer should still equal that of high CEC soils.

The soil analysis only reports the results of CEC and provides little or no information beyond that.

Your local university extension office should be able to provide specific information about conditions in your area and help further explain the soil analysis report results.

Soil analysis "active pH" and "buffer pH" results

pH means “potential Hydrogen”. The soil analysis will record two different pH tests. They include the active pH test and buffer pH test. “Active” pH is the measure of hydrogen ions in the soil at the root zone. The more hydrogen that is present in the soil, the lower the pH number and the more acidic the soil is. The less hydrogen that is present translates to less acidity and a higher number on the pH scale. Active pH is the type measured with a home soil test kit.

Not all kits are the same, so be sure the soil test kit you choose is able to test for all the things you need. The soil analysis of a home and garden soil test kit is generally not quite as accurate as a lab test. For the serious gardener or lawn care enthusiasts, these small, professional pH meters are as accurate as lab tests for active pH. Price varies greatly, so shop around.

“Buffer” pH is performed in a lab and is the measure of the soil’s resistance to change. Simplified, it means that heavier soils that are high in organic matter or clay will require more lime to correct acidity problems than sandy soils would require with the same pH reading. To explain further, a reading of 5 on the pH scale is the same for all types of soil. However, to correct the pH and bring it back to 7 would require differing amounts of lime depending on what elements are in the soil. That is what the buffer pH determines.

A couple important lawn care tips to consider: Before making pH corrections, make sure you know what pH range your plants grow best in. A home soil test kit doesn’t test for buffer pH.

Materials used for correcting pH problems

Material for correcting acidic soils

Agricultural limestone can be purchased in 50 lb bags at feed and farm stores and some lawn and garden stores. Limestone is used to make soils less acidic and bring the pH number up. When applying lime, make sure you follow the soil analysis recommendations.

The best method is to roto-till the lime into the soil before planting seed. For established lawns, lime can be applied using a fertilizer spreader and distributed over the surface of the grass. It will, however, take much longer to affect the soil pH when spread over the surface. The finer ground lime is messier to work with, but will get into the soil a little faster.

Hydrated lime is the type that is used in cement and mortar. It is sometimes used on lawns, but has a very high burn potential and is not the best choice. Agricultural limestone is safer to use, but works a little slower. Certain grasses, especially centipedegrass, are very sensitive to lime. If applied on sensitive grass, apply it in the coolest part of the year. Hot weather increases the burn potential.

Wood ashes can also be used to reduce soil acidity. Wood ashes are only about 40 percent as effective per application as limestone, but are a good choice if pH is only slightly off. Some people who burn wood have made it a practice to put the ashes on the grass or vegetable garden throughout the winter. It is not uncommon for these people to have extremely alkaline soil as high as 11 or more. This practice is not recommended because lowering the pH can take a long time.

Material for correcting alkaline problems

If the soil analysis report shows that the soil is alkaline (above 7), sulfur or aluminum sulfate is the best choice. Sulfur is an age old product, but may take months to be effective. Sulfur requires soil microbes to break it down first. Aluminum sulfate, on the other hand, works immediately and is what most professionals use.

All these products can burn the grass, so water them in well after applying.

Soil analysis results on Macronutrients

Macronutrients are the nutrients consumed by grasses in the greatest amounts and the soil analysis will usually list these first. The big three are Nitrogen, phosphorus, and potassium and represent the three numbers on a fertilizer bag. Due to the importance of these nutrients, a soil analysis report will provide amounts to apply for any soil deficiencies.

Nitrogen (N)

Nitrogen is occasionally, but not always, tested in labs. When it is tested, the soil analysis results will be shown on a scale from very low to excessively high.

The reason it is not often tested is due to the high mobility of N in the soil. Levels of N fluctuate rapidly and the analysis would not likely be accurate by the time you get the results. However, because of its importance in grass development, it is included here.

Nitrogen is the element used in the largest amount by lawn grass. It is also the element that fertility programs are based upon. When spreading a bag of fertilizer, it is the amount of N per 1000 sq. ft. that is the most important and what the application rate is based on.

Probably the two best known reactions to applications of N are grass growth and chlorophyll production. A lack of N means a slower growth and loss of chlorophyll, turning the grass a pale green color. How many times have you heard people complain that all they do is mow since they fertilized their lawn. Excessive growth from too much N is not the goal of a good fertility program and actually does more harm than good. A properly planned fertilization program will not cause excessive growth. Excessive growth is usually a problem when using the wrong fertilizer; too much immediately available nitrogen; or by applying more fertilizer than needed.

Phosphorus (P)

Phosphorus represents the second number on a bag of fertilizer. A bag of 14-3-8 contains 3% P by weight. Established lawn grasses don’t require a lot of P. The fibrous root systems of lawn grasses are very efficient at removing the P it needs from the soil. In fact, lawn grasses are much more efficient at extracting nutrients than field crops.

Phosphorus is important for proper growth and development of grasses. Its use in root development has been known and well documented for many years. Another benefit of Phosphorus is in providing increased disease resistance and improving heat and drought tolerance.

What is important to know about P is that it is relatively immobile in the soil and almost never leaches. Due to its immobile state, starter fertilizers high in P are used on newly seeded lawns to ensure enough P is directly within reach of young seedling root systems. It is not that the P wasn’t already there, but the immature root system of young grasses can’t always reach it.

Phosphorus can be harmful if it lands in ponds or lakes when it is being spread. It has the same effect on water plants and algae as it does on lawn grass- it is essential for plant development. Water plants, even undesirable ones, will get an elevated boost of internal energy, causing many problems. Phosphorus that lands on the grass next to water is not usually a problem, because P doesn’t move much once it enters the soil.

Potassium (K)

Potassium represents the third number on a bag of fertilizer. A bag of 14-3-8 would contain 8% K by weight. The understanding and the use of K have changed in recent years, as scientists better understand how the plants use it. Now we know that turfgrass uses far more K than we realized and has increased 10 fold in fertilizers. It is probably most known for how it increases stress tolerances. Additional applications of K have been a lifesaver for many sports fields by increasing the grass’ ability to withstand traffic, heat and drought problems of summer.

Less than one pound of K should ever be applied at one time to established turf.

The soil analysis results for Micronutrients

Micronutrients are nutrients consumed by grasses in small (trace) amounts. Note, however, that just because they are used in only small amounts does not lessen their importance in the health of the grass.

Boron (B)

Grass needs only very small quantities of B for healthy growth. As a result, B is rarely added to any fertilizer mixture and is rarely deficient in soils.

One problem of concern is when water from sewage or septic tanks is used for watering the grass. Sewage contains high amounts of heavy metals, and when used on your lawn, it is possible to receive too much boron. An application of fertilizer made from processed human sewage (water treatment plant sludge) such as Milorganite, will contain boron, but the concern is not great.

Copper (Cu)

Cu is used only in very small (trace) quantities. It is rarely deficient in soils and is rarely added to fertilizer. Organic fertilizers may contain traces of this and other elements. How grasses use Cu is still not completely understood. When it is present in excess, it can cause lesions on certain grasses.

Iron (Fe)

Iron is the most common micronutrient to be deficient in soils. Deficiency problems, in most cases, occur when soil pH is high (above 7). In alkaline soils, the iron becomes bound up in a form that the roots can’t take up. It is also the most common micronutrient to be included in fertilizer.

Iron chlorosis is the term used to describe iron deficiency. The symptom is a loss of chlorophyll, producing a pale green color. Iron is not a part of chlorophyll, but without iron, grass will not produce any.

If the pH is high, the additions of granular iron such as “ironite” or fertilizer containing iron will probably not help. Instead, foliar applications of liquid iron are a better choice and will provide temporary relief. This way, the iron is absorbed through plant tissues and not taken up by the roots.

Iron sulfate or iron chelates are the best sources for liquid iron. Once it is sprayed on the grass, do not wash it off. If that happens, as soon as the iron touches the high pH soil, it will change into a form that the roots cannot take up. A long term solution would be to fix the pH problem.

Iron causes rust stains on concrete, so make sure you rinse off the sidewalk and driveway after spreading.

Magnesium (Mg)

Mg is an essential element for the production of chlorophyll and is part of the chlorophyll molecule. Chlorophyll is what gives the grass its green color. Without sufficient Mg, grass will appear to suffer from chlorosis. Sandy soils are most likely to experience Mg deficiencies.

Another problem that can produce an Mg deficiency is low pH soil. Soils that have a pH lower than 7 are likely to develop Mg problems. The lower the pH number, the more deficient the Mg will be.

The easiest way to test for a Mg deficiency is to mix one pound of Epsom salt with three gallons of water and, using a sprinkling can, distribute it evenly over 1000 sq. ft. If the grass needs Mg, it will respond by producing chlorophyll with 24 hours.

If the grass responds or if the soil test shows a deficiency in Mg, then applications of Dolomitic limestone will help. Dolomitic limestone contains both lime and Mg. It will raise the pH while delivering needed Mg.

Manganese (Mn)

This element, like Fe, Zn, and Cu are needed in small amounts and are rarely deficient. Problems arise when they become less available in high pH soils. In high pH soils, the roots can’t take these elements up.

Mn is an element necessary for the production of chlorophyll. The grass will not be as green as it should. Since it is needed in small amounts, fertilizers are available with Mn included to correct this problem. The soil test should indicate if levels are low.

Sulfur (S)

These days, sulfur is rarely deficient because of acid rain. When coal and fossil fuels are burned, S is produced and distributed in rain. The amount of sulfur received each year in rain exceeds the annual turf requirement for the nutrient. About 90% of the grasses in the U.S. gets its S in this manner.

When there is an S problem, the symptom will be a yellowing of the grass. This condition will usually not change even with an application of Nitrogen. Sulfur can then be directly applied using a fertilizer spreader.

Soil analysis results for organic matter (O/M)

The quality and amount of organic matter is more important than most people might think. Most home lawns will contain 2 to 3 percent organic matter. It may seem like a small amount, but consider that a lawn with 6 percent is viewed as high in organic matter.

Organic matter is necessary for healthy soil and healthy lawns. Something you may not be familiar with is that organic matter is the primary food source for microorganisms. Soil microbes exist in tremendous numbers and breakdown soil elements into a form that can be taken up by plant roots. They are so important, that without microorganisms, plant life would cease to exist.

Unfortunately, the results shown on the soil analysis report give the percent of organic matter, but not the percent of usable organic matter. Not all of the O/M in the soil has any nutritional value for soil microbes. Applications of organic fertilizer, is a healthy part of a soil fertility program, and will ensure a supply of fresh food for soil microbes. The fertilizer on the right is a "bridge product". The 50# bag contains a large amount of organic matter made from poultry manure as well as quality synthetic ingredients for a balanced feeding. It is granulated for easy spreading with a very low organic odor.

Soil microbes are the natural enemy to many disease pathogens that live in the soil. Soils that are high in fresh organic matter have the least problems with grass diseases. Unfortunately, soil microbe information does not appear on the soil analysis report. Healthy soil is the best assurance for healthy microbe populations.

Of the different types of soil, heavy clay is probably the least favorable. It compacts easily, leaving less room for oxygen. If you haven't planted any grass, then roto-till topsoil or compost into the soil for best results. To add O/M to established turf, you can spread a layer of compost one inch thick over the surface of the grass. This is called "top-dressing" in the industry.

To step it up a notch, you can employ an additional step by using a core aerator. Core aeration (as opposed to spike aeration) pulls out a plug of soil and relieves compaction. The plugs are about 3/4 inch wide and 2 1/2 to 3 inches deep. You can either remove the cores or leave the cores on the grass to break down naturally. Core aerate heavier than usual, then cover with a 1 inch layer of organic matter. The O/M will cover the surface and fill in the holes.

Some labs may include additional information on their soil analysis reports, but for the most part, this will be it. Local university extension offices will have information on local conditions and can be of further assistance in understanding your particular soil analysis.