Soil Tests: Are They Beneficial?

Almost every gardening information lecture or class a person can take will recommend the first thing you should do is get a soil test. I have always been one of those gardeners who could not be bothered with pulling the soil, packaging and sending it off. I mean it even costs money too! I just wanted to dig in the soil and figured if plants were not doing well then they just needed more tender loving care. This was my mistake for many years. Don't let it be yours. I finally got around to pulling soil samples and packaging them up and sending them off to the University of Tennessee Soil, Plant and Pest Center in Nashville last summer after more than 30 years of gardening!

What an eye opener. I had five areas of my garden tested (garden consists of one acre of land). The areas were: vegetable garden, front lawn, back lawn, center front garden, and driveway garden. The results were a bit baffling and surprising. Baffling because soil test reports are hard to read and understand for the average lay person. Surprising because there was such a wide range of results from each area.

The results were good for the vegetable garden. The pH was perfect for vegetables at 7.2 and while phosphorous was a little high, it was acceptable, and potassium was perfect. I was not surprised because the vegetable garden gets the most amount of attention and the most 'food'. I feed this garden with compost from my huge utilitarian compost bins each year in the fall. That is my compost bin above. It is one of my great pleasures to clean out the vegetable garden by pulling the summers crop, turning the soil, adding a layer of compost and mulch and preparing for the next spring. Come spring I am all set to put in the tomatoes and seeds with very little effort on my part.

The other gardens are not so lucky to get compost each year because it is hard to make enough for my entire garden. The driveway garden started life as a driveway-full of gravel and who knows what else. Mr. Fix-it scraped out the gravel with a bobcat and moved it to the backyard. We then added trucked in soil. This garden is a challenging garden because it is under an oak tree on the eastside of the oak, so it does not get much sun at all. The soil test for this garden said the pH was 6.6 (perfect), phosphorous was low and potassium was fine. Not bad news.

The next garden I will talk about is the center garden. This garden was just 'made' last summer-the same time I took the soil sample. This garden is under oak trees and a pine tree. I had some oaks cut down in May and requested the tree cutter leave the chips right there in the middle of the yard. Over the summer they decayed ever so slightly. I then spread them all out, lined the edges of the new garden with broken concrete and had a truck full of soil brought in. I spread the soil over the oak chips, effectively creating a French drain and raising the soil level. I could not dig in this area because of the mature trees and I could not add too much soil for the same reason. The oak trees provide for air circulation and add much needed organic matter to this area. I was very interested in the soil test results from this garden. The pH was 6.0, phosphorous was low at 12, but potassium was off the scale at 320+. I called the nice people at the testing lab to ask why this was so. Remember, I had had this soil trucked in from a local trucking company. They claimed it came from a farmland. The soil testing personnel told me the soil was probably bottomland or from a farm that used a lot of fertilizer. They also said the excess potassium will not harm the plants (and I have found this to be true as the plants planted there have had more than one year to grow and are fine). What a relief.

The last two gardens were actually lawns. My entire garden is blessed with mature oak trees so the grass is challenged, to say the least. I have used synthetic fertilizers about once every other year for the past four years, I have also limed and I usually reseed every year with a good variety of tall fescue. I believe nicely maintained lawns set off the gardens and are important to the whole effect of gardens, so I spend mucho time on my lawn. The lawn was NON-EXISTENT when we moved in six years ago. The front lawn had the worst measures. The pH was a mere 4.9, phosphorous and potassium were both very low. Soluble salts measured 42. The back lawn had a pH of 5.2, and both phosphorous and potassium were OK. The soluble salts were 70. The soil test lab recommended I add 100 pounds of lime per 1000 square feet. That is a lot of lime and although I have added about 750 pounds, it is not enough. I plan to get the lawns retested before I add more. I added the lime last fall so it should have had time to take effect by now. Soluble salts were interesting to me because it is said that if you use synthetic fertilizers then soluble salts can build up in a lawn and harm them. Additionally, synthetic fertilizers can decrease the pH of your soil. I theorize this is the reason the lawns are so acidic. Lawn grasses need a pH of between 6-7 to do well.

You can be your own judge of whether or not a soil test is worth having. If your gardens are growing fine with minimal help then you probably don't need a soil test. But if you, like me and most gardeners, have problems with a specific type of weed or your grass and plants are not growing as well as you think they should be and you have met all cultural requirements, then you too should have your soil tested. I have found the trouble and expense well worth it. The local extension office will have small bags for the soil and instructions for mailing the soil. They will also send it in for you but it is far cheaper to send the samples in yourself. Everyone should have at least one soil test done on their property just to see where they are starting from and what they have to work with.

in the garden....