“Dirt is in my vacuum cleaner,” said Dennis Ryan, professor of arboriculture at UMass Amherst, addressing a meeting of landscape professionals, “we work with soil.”
This opening line, which was used more than once in my recollection, always brought a chuckle from the crowd, but his statement was well taken by the audience. As industry professionals, it was understood where this speech was going… stay focused on the science and the fundamentals. Ryan’s point was that there is a lot more to soil than most of us think, and he was right.
Loam is probably the most familiar type of soil we use on a regular basis. It’s really a mixture of sand, silt and clay, with a bit of organic matter sprinkled in. The organic matter component isn’t technically necessary for it to be called loam, but it is an additive essential for great plant development.
Sand, silt and clay are particles of varying sizes derived from rocks that are in their final stages of decomposition or erosion. As the larger rocks erode, they expose minerals that become available for our plants. In addition to these minerals, plants need other nutrients that they acquire from incorporated organic matter and from photosynthesis. We can add fertilizer to re-create what Mother Nature does naturally, or we can take a cue from her. She adds the right amount of organic matter to the soil every year when the leaves fall off the trees in autumn. As the seasons progress, the stored energy in the leaves is transferred into the soil, where it waits for use by our plants. Too much organic matter and the soil doesn’t drain properly; not enough and the plants lack essential nutrients.
So what’s the right balance in the landscape? In the horticulture industry, there’s a lot of guessing going on when the answers are just a soil sample away. Many times we get called to assess PPP, or poor plant performance. So one of the first things we do is check the soil. Testing the soil can range from a simple pH probe to an analysis that gives us a detailed report on the composition of the soil so any issues can be corrected.
UMass and the University of New Hampshire both offer these tests for a nominal fee and will take the guesswork out of the equation. I’ll give you an example. Let’s say my hemlock was looking a bit yellow, instead of the dark green it typically displays. We call this condition chlorosis, and it may or may not be caused by an iron (mineral) deficiency. So we add some iron, right? Not so fast. The soil sample comes back with an acceptable iron level, but the pH is way off. Hemlocks, along with most evergreen plants, need a soil pH in the acidic range, something less than 7, and our sample indicates our soil pH is too high. So instead of adding iron, we need to adjust the pH so the iron that is in the ground can be used by the plant. There’s no way anyone’s coming to that conclusion without a soil sample!
Good horticulture is all about understanding the needs of the plants you’re trying to grow. Mother Nature has given us the road map to great soil, but somewhere along the path we lost our way and now insist on new ways to solve our problems. It may be easy to buy some fertilizer at the garden center and sprinkle it onto our plants when they look yellow, but it might do more harm than good. A steady diet of good soil, a long drink of water about once a week, and some bright sunshine are all that a plant really needs.
Understanding soil is ultra critical to successful horticultural practices, but is often ignored because it is out of sight. Just like a balanced diet is essential to our good health, plants depend on the soil to support them both physically and nutritionally. The time, energy and effort required to get a proper soil test done is minimal when you understand the long-term benefits of great soil, because it’s not just dirt.
Don’t Call My Soil Dirt
This opening line, which was used more than once in my recollection, always brought a chuckle from the crowd, but his statement was well taken by the audience. As industry professionals, it was understood where this speech was going… stay focused on the science and the fundamentals. Ryan’s point was that there is a lot more to soil than most of us think, and he was right.
Loam is probably the most familiar type of soil we use on a regular basis. It’s really a mixture of sand, silt and clay, with a bit of organic matter sprinkled in. The organic matter component isn’t technically necessary for it to be called loam, but it is an additive essential for great plant development.
Sand, silt and clay are particles of varying sizes derived from rocks that are in their final stages of decomposition or erosion. As the larger rocks erode, they expose minerals that become available for our plants. In addition to these minerals, plants need other nutrients that they acquire from incorporated organic matter and from photosynthesis. We can add fertilizer to re-create what Mother Nature does naturally, or we can take a cue from her. She adds the right amount of organic matter to the soil every year when the leaves fall off the trees in autumn. As the seasons progress, the stored energy in the leaves is transferred into the soil, where it waits for use by our plants. Too much organic matter and the soil doesn’t drain properly; not enough and the plants lack essential nutrients.
So what’s the right balance in the landscape? In the horticulture industry, there’s a lot of guessing going on when the answers are just a soil sample away. Many times we get called to assess PPP, or poor plant performance. So one of the first things we do is check the soil. Testing the soil can range from a simple pH probe to an analysis that gives us a detailed report on the composition of the soil so any issues can be corrected.
UMass and the University of New Hampshire both offer these tests for a nominal fee and will take the guesswork out of the equation. I’ll give you an example. Let’s say my hemlock was looking a bit yellow, instead of the dark green it typically displays. We call this condition chlorosis, and it may or may not be caused by an iron (mineral) deficiency. So we add some iron, right? Not so fast. The soil sample comes back with an acceptable iron level, but the pH is way off. Hemlocks, along with most evergreen plants, need a soil pH in the acidic range, something less than 7, and our sample indicates our soil pH is too high. So instead of adding iron, we need to adjust the pH so the iron that is in the ground can be used by the plant. There’s no way anyone’s coming to that conclusion without a soil sample!
Good horticulture is all about understanding the needs of the plants you’re trying to grow. Mother Nature has given us the road map to great soil, but somewhere along the path we lost our way and now insist on new ways to solve our problems. It may be easy to buy some fertilizer at the garden center and sprinkle it onto our plants when they look yellow, but it might do more harm than good. A steady diet of good soil, a long drink of water about once a week, and some bright sunshine are all that a plant really needs.
Understanding soil is ultra critical to successful horticultural practices, but is often ignored because it is out of sight. Just like a balanced diet is essential to our good health, plants depend on the soil to support them both physically and nutritionally. The time, energy and effort required to get a proper soil test done is minimal when you understand the long-term benefits of great soil, because it’s not just dirt.
Visit either the UMass or UNH websites for detailed information on how you can submit a soil sample:
http://extension.umass.edu/agriculture/index.php/services/soil-tissue-testing-lab
http://extension.unh.edu/Agric/AGPDTS/SoilTest.htm