Soil Testing Semi-Simplified

Matthew Doyle, assistant editor

A wide range of testing costs are possible, with some university extension labs (depicted) offering some free testing. However, in Dr. Mike Kernan's (with Plant Health Inc.) experience, these services are usually only free to homeowners and agricultural clients. Another potential problem with this route according to Fesko is their frequently basic nature, which may not provide needed information.

Assuming money is no object, modern soil testing (teamed with tissue samples) can take most of the guesswork out of plant care. However, money is very much a concern to the landscape contractor, particularly in today’s economy. So what are the benefits vs. costs, and how do you get dependable results?

Sample collection equipment can be as simple as a spade, particularly if dealing with level, historically undisturbed areas. According to Engberg, little localized differences in soil can be expected and samples from several locations totaling about one pound can simply be mixed into one bag. However, if unsure whether the soil has been disturbed in the past or the terrain is hilly, the likelihood of very localized differences precludes this technique.

Testing Benefits

First off, as Jeff Fesko of John Deere Landscapes put it, soil testing cuts right to the chase. There's no guesswork involved in determining whether a nutrient deficiency is present, you can simply see it in numbers. As a result, the potential to throw hundreds of dollars at a problem hoping for a solution only for it to prove continually elusive is greatly reduced. The probable time spent searching for a solution is reduced as well.

Fesko also considers the technique a helpful business tool. He notes the landscape contractor using soil testing can point to hard data as a basis for recommendations if the customer inquires. More specialized or targeted amendments and subsequent services can be professionally recommended in good faith and with solid data. Finally, the consistency and potential immediacy in results that testing encourages can better support long-term customer satisfaction, retention and referrals.

Commercial labs (depicted) are another possible testing source, and Jack Engberg of Gro-Power claims costs typically range from $50 to $200 for a general analysis. However, specialty tests for exotic toxins, soil permeability and other less common data points can raise this cost substantially. Another source of increased cost can be sample collection by a lab technician, but 30 year-veteran Engberg only recommends this route if you suspect a visual inspection by the technician might shed light on an unusual problem.

Portable testing kits are another option, and costs range from five dollars for a basic Ph test into the thousands for very extensive kits according to Engberg. Some of the more basic kits have great cost savings potential if basic data is all that's needed. However, Engberg agrees the more expensive options (which he points out are usually slightly less capable than a lab) are only a worthwhile investment if doing very frequent testing requiring immediate results.

Testing Costs

This depends on how extensive the testing is and whether an extension office, commercial lab or do-it-yourself kit is used.

A final option is portable kits you can use yourself. Engberg described their costs as anywhere from five dollars for a basic ph test to $1,000s for kits cable of very substantial testing. However, he claimed even these higher end options are usually slightly less capable then labs. Some of the lower cost kits certainly have money-saving potential when more basic data is needed. However, Engberg agrees with the editor that investing in some of the more extensive and expensive kits is only worthwhile if very extensive data is needed very frequently. An example might be a landscape contractor frequently dealing with very challenging soil and/or water quality concerns needing constant monitoring and fertilizer adjustment.

Among the first steps in selecting a quality lab is reviewing a facsimile report. Engberg advises you look for a quality analytical page with raw data numbers, an interpretative page like the one depicted with graphics explaining the results and a recommendation page offering specific product recommendations as opposed to pounds per thousand square feet. The latter is common from more agriculturally oriented labs.

The final testing equipment option is a soil probe or core sampler, and it offers similar benefits to a profiler. As the graphic points out, it's key that a useful sample is collected. Obtaining material from the root zone (often 6” down or deeper) for the plant involved is a key. Also obtain as many samples as possible in as many places as possible (15 to 20 may be excessive in residential settings), covering zones with both healthy and un-healthy vegetation.

Balancing Benefits & Costs: When to Test

The benefits of soil testing make it's use as often as can be afforded prudent. More specific information requires that individual contractors examine their budgets, potential testing costs and benefits/savings and how these considerations impact profits and how competitive resulting bids are. However, testing is particularly useful in several situations.

What if you can't afford to test in a given situation? 16-year industry veteran Dr. Kernan recommends a broad-spectrum fertilization approach utilizing fast release, slow release and biological components. The fast release component provides immediate results to make the customer glad to have given you their hard-earned cash. If done in minimal amounts, leeching problems are discouraged. The slow release component provides long-term nutrition, as it slowly becomes available to the plant. Finally, organically derived products, including bacteria and mycorrhizae fungi fertilizers that have become available in roughly the last 10 years substantially increase the efficiency with which nutrients are absorbed. They can also make soil nutrients available that would otherwise be in un-soluble and otherwise inaccessible forms. Note that using soil testing to guide the proportions in which the various nutrient components are applied in this integrated approach is still ideal.

A soil profiler is another sampling equipment option. This option allows the landscape contractor to get a visual perception of soil layers. Permeability options associated with clay or similar problems can be diagnosed as a result. This tool is also useful for collecting point samples at sites where large localized variations in soil type are expected.

Selecting a Lab

First off, ask for a facsimile report to examine. According to Engberg, labs tend to specialize in either agricultural or landscape testing. The biggest giveaway is how recommendations are expressed, in pounds per thousand square feet (agricultural), or in specific products commonly available to provide the appropriate nutrient mix (landscape). Regarding overall report layout, Engberg and Fesko claimed a quality report should start with raw data representing the various soil properties. Second up should be an interpretive explanation of the analytical data, usually with graphical representations of nutrient deficiencies and surpluses. The final section should provide recommendations based on the interpretations in a landscape format as discussed. All this information should be clearly legible and explainable to customers.

Finally, take the time to find a lab that meets all the aforementioned criteria within your price range. Then simply follow the application directions on the label of the labs recommended product (or one offering a identical nutrient mix). Engberg recommends the same source for gauging when to expect results.

A major benefit of soil testing for the whole green industry is reduced fertilizer leeching with precipitation events. The excessive nutrient levels in waterways that can result promote massive algae and plankton blooms like the one depicted. The ecological damage that follows encourages further fertilizer bans and restrictions, something the industry as a whole can discourage with proper application amounts as determined by soil testing.

Fertilizer Burn

He also had a couple tips for avoiding fertilizer burn. The biggest is to simply not over-apply. Also be wary of heavy fertilization in high salinity soils. Finally, thoroughly water-in fertilizers unless performing a foliar application.