Josh & Bahiyyah weigh in on soil testing
Most problems found in trees are not the result of pesky bugs or diseases, as one might think, but rather stem from somewhere far more basic and unsuspecting: the soil.
Urban soils are notoriously tough on trees. Soil compaction, containments, nutrient deficiencies and unbalanced pH levels are just some of the problems trees face in urban environments. As Josh Singer, a resident Casey Trees Urban Forestry Crew member, explained in our most recent Tree Talk Thursday: “D.C. has a lot of different soils, but it’s typically known for its clay soil – the same clay from which the bricks of Georgetown were made. Most urban soils lack any kind of organic layer, denying it of naturally reoccurring fertilization. Instead of an organic layer, urban soils typically have turf, rocks, bare ground, or other hardscapes as its top layer. This can cause of series of problems.”
But often times the hardest part of dealing with soil problems is diagnosing them in the first place. That is why Casey Trees recommends performing a soil test both before and after you plant a tree.
To get an accurate reading from a soil test, follow these simple tests:
- Dig about six to 12 holes, six to eight inches deep, in each unique area.
- Scrape the side of each hole to get a sliver, six to eight inches long.
- Put all the slivers together in a bucket and mix thoroughly, making sure to remove any grass, rocks or debris.
- Scoop out a cup of soil and dry it out in the sun.
- Place the dried soil in a labeled plastic bag, mail it in a box to a soil testing facility and wait for the results.
Bahiyyah Parks, a local expert on soil and the second contributor to our “soil” Tree Talk Thursday, added some helpful testing hints during our conversation:
- “When identifying unique areas, look for: discrepancies in different top layers (turf, bare soil, hardscapes), different elevation levels, if rain water is running off into one area but not another, if there are dividers such as sidewalks or roads, etc.”
- “The cheapest lab I’ve found is at the University of Massachusetts’ Amherst lab, at http://www.umass.edu/soiltest/. It’s ten dollars for a full test, including heavy metals.”
When the soil test results come back, they will have a series of recommendations. For example, if your soil’s pH level is too high – alkaline – or too low – acidic – it means the roots of your tree will not be able to properly absorb nutrients. Adding lime can increase the pH level while adding sulfur can decrease it. However, if your soil has high levels of heavy metals, you may have to replace it or add sufficient amendments to dilute the containments.
If your soil reads low on nutrients, you can either add fertilizers or organic matter, like compost. Bahiyyah Parks believes “there’s a nearly limitless supply of organic matter you may add to your soil to improve it,” to aid with things like: nutrient levels, water retention capacity, soil structure aggregation (attempting to increase water infiltration and prevent soil compaction), balancing pH levels, and preventing soil erosion. Josh Singer is in favor of organic matter as well: “Amending with organic matter (as opposed to fertilizer) has many advantages, because it’s a slow release fertilizer – which prevents runoff and leaching of the nutrients, and root burn (where fertilizers can suck water from tree roots).”
While protecting your trees from pests and disease are always important, remember that often times the root of the problem starts in the ground. By following these easy steps you can save yourself (and your tree) a lot of hard work and effort down the line.
This post was added to from the version originally featured in our e-newsletter, the Leaflet. Subscribe to get the Leaflet delivered to your inbox every month.
Photo credit: Travis S.
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