There are many reasons to soil test, says Tracy Allen, lab supervisor at the UMass Soil and Plant Nutrient Testing Laboratory in Amherst, Massachusetts.
The first two may seem obvious: soil tests allow contractors to monitor both nutrient levels and acidity, or pH, levels of the soil – attributes that are key in the health of turf as well as annual and perennial plantings – and adjust them as necessary.
“All plants need nutrients to grow, but you have to monitor the soil to make sure they’re not over-fertilized or under-fertilized,” Allen says. “In terms of the pH, or acidity, plants have what we call a sweet spot of around 6.5 to 6.8 on the pH scale where they do the best at nutrient uptake, so you want to know the pH of your soil and adjust as necessary.”
But there are also significant environmental, financial and health reasons to soil test, Allen says.
The pH of a location’s soil helps determine the proper treatments.
Photo courtesy of UMass Soil and Plant Nutrient Testing Laboratory
As an environmental protection, many municipalities across the country have enacted restrictions against overuse of phosphorous and nitrogen-based fertilizers, and some areas now require soil tests to first establish the need for the fertilizer before it’s applied.
From a cost-savings perspective, soil testing can boost your company’s bottom line, since it helps prevent the purchase and application of fertilizer when it’s not needed.
If you’re still not convinced that soil testing is necessary, consider this: Implementing soil testing in your routine service plan can help boost clients’ perception of your firm’s competence and expertise, says Chuck Darrah, consulting landscape agronomist at CLC Labs in Westerville, Ohio. “Soil testing is not only environmentally responsible; it also shows your professionalism.”
Because soils differ so greatly from one part of the country to another in terms of texture, acidity, and makeup, it’s best to partner with a soil testing lab in your region when possible. Many universities provide standardized soil sampling protocols tailored to their specific climate, says Bruce Hoskins, assistant scientist at the Analytical Lab and Maine Soil Testing Service in Orono, Maine.
“The soil testing methods really depend on the types of soil and the climate you’re dealing with in that part of the country,” Hoskins says. “East of the Mississippi, where there’s pretty adequate rainfall, soils tend to be naturally acidic and the test methods are geared accordingly. Out West, the soils tend to be increasingly alkaline and saline, and the test methods are going to be designed to check for that and make recommendations for compensating for that.”
If a university soil testing lab isn’t available in your area, search for commercial labs that regularly exhibit or attend green industry conferences or trade shows, Darrah says.
The staff at reputable soil testing labs are typically happy to serve as best-practices resources for clients in their region. “People can call or email us if they don’t understand the recommendations or if they just don’t understand the results,” Allen says. “I talk with clients about their soil results all the time, and it’s a part of the job that I enjoy most.”
“Soil testing is not only environmentally responsible; it also shows your professionalism.” Chuck Darrah, CLC Labs
How often to test.
To stay abreast of what’s going on in the soil you’re servicing, plan to soil test routinely.
If you’re working with a new space or are still in the process of identifying optimum fertilizer levels for a particular client, you may need to test as frequently as once a year until plants become established. “If you’re still trying to figure out the levels that your particular lawn needs, it’s good to have an annual soil test. But once you figure out the levels that the area needs, you can test every two or three years,” Allen says.
Above all, don’t make the mistake of using soil testing only as a post-mortem response in the event of plant failure, Hoskins says. Ideally, you should soil test before planting.
“If you’re putting in a new lawn or a new bed of foundation plantings, it’s really important to check the soil before you plant to make sure it is healthy enough to support plant growth,” Hoskins says. Then test again six months to a year after installation. “If everything is OK after that, a maintenance-type application would include testing every two to three years or so – unless you’re dealing with a golf course and greens, which typically test every year,” Hoskins says.
The point of repeated testing is to understand the ongoing interplay of the plants and the soil over time.
“Perennials will modify the soil as they grow,” Hoskins says. “It’s not just the soil feeding the plants, but the plants also feeding the soil.”