Getting Good Soil Test Results


How to test, analyze and interpret the data

Photos Courtesy of Brookside Laboratories.

Testing for moisture retention and pore spaces is a crucial element of looking at turf soil structure.

For some idea of the complexity, and importance, of the soil test in relation to turf health, talk to a soil scientist or a test laboratory manager. The whole process begins to take on the air of a bizarre nightmare of complexity and, to some degree, chance, especially if the test is not interpreted properly. It can also exist, in the hands of some, solely as a means of selling products.

OK, digging up some dirt and putting it in a plastic bag is not difficult. Neither is sending it to the lab. But, which bit of soil do you send, what tests among the thousands available do you request, and how do you read the results? More importantly, how do you interpret that information, all in the form of chemical and soil structural numbers and percentages, into soil and fertility recommendations?

There are three ways to conduct this operation: the turf manager can learn to do it himself; an independent consultant can be hired; or a consultant affiliated with a laboratory can be utilized. Because a soil lab report is specialized information that relies on a knowledge of chemistry, soil structure, geography and turf needs, professionals should be involved and an accredited lab should be used.

Bob Carrow, professor and researcher in the crop and soil science department at the University of Georgia, says that if a professional turf manager learns to conduct and interpret soil tests himself, he will retain control of the situation and get an unbiased analysis. That’s because the soil test is one of the crucial aspects of turf management, and decisions are most relevant when made by the on-site manager.

“I would say soil tests have increased in importance over the last several years, and will continue to increase in importance,” Carrow says. That’s because, in many turf-growing parts of the country, water quality is worsening over time. As more poor-quality water is used, soil quality changes and requires adjustment. Not only are soil tests more important, they should also be used more frequently.

Ironically, Carrow says, on sites where water quality is good, the soil test is the most important test that can be performed. On sites where water quality is poor, a water test is most important. In either case, both soil and water tests should be taken and weighed against each other. Tissue tests are also important in turf management, but they only give a snapshot of fertility status that can be used in diagnosing problems. A soil test, on the other hand, is predictive.

There are two kinds of soil tests, Carrow points out, and both can be important. The chemical test is the more standard test, and is used to look at nutrients available to the plants. The physical test looks at soil structure and can be indispensable when a turf facility is under construction, is suffering from ponding or turf thinning, or when there are salty soils and water.

“Turf managers need to learn how to read soil tests,” Carrow says, and how to collect them, because there is an entire industry of salesmen and consultants out there poised to take and interpret their soil for them. He has seen many of these “bogus” consultants during his long tenure as a soil scientist, and too often their aim is to sell soil amendments or fertilizers.

Carrow says it is easy for biased consultants to manipulate or misinterpret test information. Thus, he argues for a turf manager to take his own soil samples and interpret his lab reports. He adds, however, that this is a complex field with many controversies—such as the one over whether nitrogen can be tested at all in the soil, and the one over whether the Base Cation Saturation Ratio (BCSR) method so often used for turfgrass soil testing is less effective than the Sufficiency Level of Available Nutrient (SLAN) method.

Carrow acknowledges that a turf manager may not be able to carry out these chores himself, and may want to use a consultant. Carrow recommends that he find one who will be able to explain the rationale behind lab techniques used. That’s a quality control test for the consultant. He says that one benefit of a qualified consultant is that he could provide an independent analysis and detailed descriptive reports.

An alternative would be to find a reputable laboratory that has its own list of affiliated turf consultants. This gives the manager not only a reliable lab, but proven consultants who deal with it. Since these consultants work for fees and not for fertilizer or amendment companies, they will hopefully provide unbiased results. One such lab/consultant affiliation is Brookside Laboratories, Inc.

“There’s no right or wrong soil test,” says Mark Flock, director of the Brookside lab in New Knoxville, Ohio, and a certified soil scientist. He says his and other labs offer literally thousands of tests for soils, plant tissue and water, and each is applicable to some plot of turf someplace. Which test is applicable to your specific turf and soil type and location given your water quality and desired plant growth patterns? That test selection should be left to a person knowledgeable in all of those subjects, as well as to your needs.

Flock, who has been at this for a long time, says the Brookside model is to train and utilize independent consultants. Brookside has some 250-plus affiliated consultants, and they are all over the world. Not all are turf specialists, since the lab also serves agricultural and environmental clients. Whether a turf manager uses Brookside or not, Flock suggests that he work through an American Association for Laboratory Accreditation-listed lab for all geotech testing. Several are listed at the USGA Web site at, though not all of those listed do both physical and chemical testing. Good chemical testing labs usually participate in North American Proficiency Testing, though this is not an accreditation program.

This method is viable because an accredited lab and trained consultant will provide quality work, and also because it’s “comparing apples to apples,” Flock says. A consultant who becomes familiar with your turf and soil types, and a lab that gives verifiable results, will get to know your site and be able to track soil and turf over a period of time. Over the years, both the consultant and lab get to know the goals of that facility. Brookside ( tests over 3,000 golf courses and other turf facilities annually.

Flock explains that a facility may require both types of soil tests: chemical tests that analyze the chemical components, including nutrients, in the soil, as well as soil structure tests that analyze elements that make the soil friable, give it air-holding capacity and provide good water penetration. Any number of plant problems, as well as diseases, originate in the soil. Develop a consistent nutrition program in order to address turf problems that arise and to meet nutrient management plans recommended or mandated by some states.

“You need to know what’s in there,” Flock says. His mantra is: “You cannot manage what you cannot measure.”

Flock gives examples of how a soil structure or construction test is valuable. Let’s say your turf shows signs of thinning. There may be soil layering or compaction, leading to poor water drainage. These elements can be measured in the lab, through the use of a sand fractions test that detects

coarseness of soil particles, and through tests that detect total air pores and capillary pores. Turf roots will not be healthy without good oxygenation, and the USGA has recommended percentages for air pores in greens. Those can be determined in the lab, and a good consultant can recommend how to achieve them in the field.

One of the most important components of soil is the organic matter, usually as a percent of the sample, and soil tests can determine that on a weight basis. Flock says there is no ideal recommended amount of organic matter, but a good consultant can provide a recommendation based on the individual site and turf type. He can also determine whether there is a black layer (an anaerobic layer of organics) that is stopping root growth.

Chemical tests are many and varied, Flock says. A basic one is a soil fertility test for extractable minerals. Many tests can be chosen to examine fertility, because each soil and turf type, as well as each region of the country, calls for specific tests. The same tests used for the acidic soils of the East may not be the most appropriate for the alkaline soils of the West. All the more reason to work with a consultant who works closely with one lab, Flock says.

This can make nutrients, and testing, cost-effective. Flock points out that a typical golf course may order several tests a year. A new course should employ a soil test on every green and as many as two or three per fairway the first year to establish a baseline. In following years, tests can be done for representative sectors of the course and in any problem areas.

The third type of relationship is with a consultant who has no specific affiliation with a lab. Completely independent, he is totally on the turf manager’s side. Located in San Antonio, Texas, Ron Duncan is a consultant and vice president of Turf Ecosystems. Since his retirement from the University of Georgia, he has traveled the world analyzing turf and correcting problems. He deals with many labs, and helps turf managers interpret lab reports and implement changes.

A robotic pH analyzer is only one of many pieces of equipment used by an accredited soil testing laboratory.

“All of my recommendations for my clients are going to be based on science,” Duncan says, and without soil, water and tissue testing there is no way to acquire that information. The client can pull the test, using a standard soil tube, or Duncan can pull it. The trick is in interpreting it. “When I’m dealing with golf course greens, I’m really a stickler for information.”

With so many saline soils and water sources, for example, a soil test is indispensable in determining the salt/soil interaction. He agrees with Carrow that it would be good policy for turf managers to be able to read these lab reports themselves. However, few can, he says, even college graduates in turfgrass management usually do not get proper training in this area.

He recommends that if a grass grower wants to be able to interpret this data and use it properly on his site, he should take a workshop or seminar. It may take more than one course, because it’s not a matter of simply learning what the symbols mean. It also means learning the scientific method inherent in correctly interpreting reports and using that information to make beneficial management adjustments. “It goes back to basic management,” Duncan says.

One of the chief goals of a turf manager should be the avoidance of unskilled or biased consultants. Duncan says much of his work, inside and outside of the United States, comes to him because a facility has used products recommended by salesmen and so-called consultants, who interpret lab data into the use of their specific line of products. He has no set list of products, and, in fact, goes to great lengths to find the scientific basis for their use before recommending them. He also wants to see proof that they have worked in the real world. Red flags should go up when being “sold” rather than being “educated.”

Duncan says the best way to find a good consultant is word-of-mouth. That’s how he gets most of his work. Turf managers should use their professional associations and networks to talk to their peers and find consultants who have been successful in correcting soil problems. Keep lines of communication open with people who have facilities and problems similar to your own. Do your homework.

Don Dale is a freelance writer and a frequent contributor. He resides in Altadena, Calif.