A soil with a balanced pH perfect for healthy lawns and produce can be achieved with information received from a laboratory soil test, which can also show nutrient levels present in the earth.
Although it’s currently winter in Clark County, spring and the growing season will come. That means for those looking for good yields on their vegetable gardens or an attempt at a perfect lawn it might be time to think about getting your soil tested.
Soil tests can show the nutrient content and acidity of dirt for gardeners. Although generally the soil in Clark County is fairly viable, there are a few cases where testing might be beneficial, said Martha Minnich, a Clark County Master Gardener with a PhD in soil chemistry.
The soil in Clark County is fairly good for growing, Minnich said. Although mineral deficiencies aren’t too much of an issue, the largest area of concern is with soil pH, as the region tends to have more acidic earth (a lower pH).
In order to balance out the pH to make it more conducive to growing vegetables, fruit trees or healthy lawns, lime is used as a soil amendment, Minnich said. Just how much lime to use is important, as adding too much can cause the soil to become alkaline, making some mineral deficiencies more likely, she said.
Knowing what the test is designed to do is important, as some growing issues arise from things other than nutrient and pH needs. Minnich said that around the region individuals tend to complain about “heavy” soil, for which a soil test wouldn’t do any good — the likely culprit is the earth is too compacted.
“If your plants don’t grow well because you compacted the soil, there’s no soil test that’s going to help you with that,” Minnich said.
A soil test might be beneficial for those who notice their grass isn’t growing well, Minnich said. Grass seems to have trouble growing in the region, she explained, due to a tendency for grass varieties to favor a more neutral pH.
As far as actually conducting the test, those looking to do so in the spring will likely encounter wet earth, Minnich said, so making sure not to inadvertently compact the soil by driving over it or heavy footsteps is important.
Minnich said to collect samples with a shovel in a couple of different areas, but only the areas planned for some sort of amendment. When collecting samples, getting soil at rooting depth, which differs from plant to plant, is integral. Trees generally have deeper roots than vegetables, Minnich said.
After collecting, gardeners should put the soil sample in a zippered plastic bag to be sent off for testing. When it comes to the actual test, Minnich suggested A & L Western Agricultural Laboratories, which has a facility in Portland.
Washington State University Extension recommends A & L, Minnich said, because their tests were more tailored for Western Washington than facilities on the eastern side of the state where the soil composition was different.
The complete analysis that A & L provides, as well as a graphical report and recommendations, runs about $36 according to information from the laboratory’s website. Minnich said the recommendations are important for gardeners as the analysis can be technical.
One of the benefits of the recommendations from the lab is information about the buffer pH for a soil, which shows how much of a soil amendment like lime that needs to be added to get the soil balanced.
Although there are do-it-yourself soil testing kits on the market, Minnich was leery about relying on them, as in her experience she has seen suspect results. A need for accuracy also merits having a lab test done, so when it comes to analysis it’s best to go for the complete package.
“You care (about) the difference between 6.5 and 5.5 (pH) a lot when you’re growing vegetables,” Minnich said, explaining that DIY soil tests tended to not have the accuracy needed for hitting the pH sweet spot.
In addition, having a lab analysis with recommendations can help demystify what all the data mean.
Although the process of collection and getting a lab test done might seem a bit of an ordeal, for those looking to maximize their gardens the analysis could be vital.
“If you are really fussing with your grass, then you’ll probably send off a soil sample,” Minnich said.
A detailed list of information for soil sampling, as well as the address for A & L’s Portland and Modesto labs, is available at
al-labs-west.com/extra-pages.php?section=Soil%20Analysis.
