SOIL TEST RESULTS ARE IN. DID I PASS?

The results of the soil tests of the skinny bed next to the house and what I call the main garden just off the patio came were not what I would call earth-shattering, but ironically the one thing I thought I knew is probably what I was most wrong about.

One of the reasons I wanted to test the skinny garden alongside the house is because I feel like plants just aren't flourishing there like they should be. I plan to renovate that whole bed this spring, pulling out almost everything and starting mostly from scratch, but before I invest the time and money in doing that I wanted to make sure there's nothing odd going on there, like something leaching from the foundation into the soil.

Here are the results from that bed.

So what does it all mean? Let's break it down.

The levels of nitrogen, phosphate and potassium are not a big surprise. You can't really accurately measure nitrogen levels outside of the growing season and since nitrogen levels change constantly as it is being used by plants or becomes tied up in organic matter, it can be difficult to really know what's going on with nitrogen. Most gardens can use some supplemental nitrogen at the right time of the year. It's not a good idea to add nitrogen early in the year when you need plants to concentrate energy into root growth or at the end of the season, when a flush of leafy growth may not harden off in time to deal with winter.

Most gardens also have adequate levels of potassium and phosphorus and you can see that the levels are off the charts in this section of mine.

The organic matter level is at 7.6%, which is pretty good (you don't want this number to get above 10% and it's important to remember that the more organic matter, the more it ties up nitrogen in breaking it down).

But the number to look at is the pH; the one number I thought I had a good handle on before doing this test. At 7.5, my soil pH is definitely higher than I thought it was (I was under the impression that it was more in the 7.2 range). A pH of 7 is neutral. Anything below that is considered acidic, anything above it is alkaline. And while a lot of plants can handle a range of pH, 7.5 is definitely at the high end for where plants will thrive.

For instance, I continue to attempt to grow a climbing rose in this bed and although they grow, they don't thrive like they should given that it is nearly perfect conditions for them. The last few years they've also suffered from aphid attacks, which is in my opinion a sign of a less-than-healthy plant. The optimum pH for roses is 6.5.

The other problem with high pH soils is that they can make it difficult for plants to use micronutrients in the soil. One of the recommendations in the report addresses this. "Some ornamentals such as roses may show yellowing (chlorosis) from iron and/or manganese deficiency at high soil pH. Treat problems related to micronutrient deficiency when soil pH is above optimum with foliar spray containing iron and manganese 1 to 2 times during the growing season."

The results of the main garden test showed similar results.

The pH is just a touch lower and the organic matter just a touch higher. I've been having a few issues with cholorosis on my large Limelight hydrangea in this bed and I now think that's due to it needing some micronutrients because of the high pH.

There is a difference in texture between the soil sample from the skinny garden, top, and the main garden, bottom.

There's more to soil than just numbers of course. Another helpful test I could do at home would be to do the soil-in-a-jar test that most of us probably did in school to determine texture and composition. Fine Gardening has information on how to do a more elaborate version of this test. Just from looking at my soil samples it was clear to me that when I rejuvenate the skinny bed I need to work on creating a more moisture retentive soil.

So what's the bottom line here?

1. There's no need to seek out balanced (i.e. 10-10-10) fertilizers because my soil doesn't need any more phosphorus or potassium than it already has. I can spend my money concentrating on just adding nitrogen.
2. More than fertilizing, I need to be focused on bringing down the pH of my soil. I'll never grow azaleas, but I think I can make some serious strides to getting the pH closer to neutral. There are two main ways I can achieve this: aluminum sulphate or elemental sulfur. Elemental sulfur will require less but will take longer to work. Aluminum sulphate works faster but requires about six times more to get the same pH change of elemental sulfur. 
3. I need to consider incorporating an iron or manganese foliar spray for plants showing signs of chlorosis. 

Will I recoup the $30 I spent on the tests? Probably, although even if I didn't, knowing what I need to do to improve my garden would be well worth the $30.

STOP! BEFORE YOU TOUCH THE GARDEN, DO THIS

Before you add anything to your soil or plant anything in your garden this year, answer one question:

When was the last time you had a soil analysis done? Five years ago? Ten? Never?

Soil analysis tests are an investment—usually $10 to $15—but I can almost guarantee that you will recoup that money several times over by not adding things to your soil that it doesn't need.

Just to be clear, I'm referring to a soil analysis done by a lab, not one of the little kits you pick up at the hardware store where you mix something that resembles and Easter egg dyeing kit with tiny bits of soil. I think those are probably better than nothing and are a bare minimum if you are gardening in a new place. Of all the things you need to know about your soil, the acidity level is the most important in my opinion, and those little kits can give you a pretty good idea of where that is at.

When you take a soil sample, dig down about 4 to 5 inches and sample from several places in your garden. 

Most labs that do soil testing focus mostly on agriculture testing or environmental testing for things like Chromium ("Erin Brockovich," anyone?), but they also do simpler tests aimed at homeowners. But you won't necessarily hear about them until you go looking for them.

To my knowledge, every state has a public university extension program and they will either be able to test your soil at a state lab or give you a list of labs that do the testing (if you're in Canada, here's one list of soil labs I found). Just do an Internet search for "University of (your state) extension" and once you get to the extension website, do a search for soil test. If that fails you could search for a nearby state's lab and ask if you could send your sample there.

It's important that you take a sample properly. Some labs provide sample bags but most that I know of are fine with a sample in a regular old Ziploc bag (well, actually a new bag because you wouldn't want anything else contaminating your sample).

A Ziploc bag works fine, but some labs also provide wax-lined sample bags.

When it comes to taking a sample, don't be greedy. Different areas of your yard could have very different soil depending on fill that might have been used, what has been growing there, or how you've amended the soil over the years. So stick to an area that you anticipate will have consistent soil. You want to take small samples from about five different areas within a bed (assuming you've identified that as your test area) for a total of about 2 cups of soil. A trowel will do just fine for this job. Just dig down to about 5 to 7 inches below the surface and bring up a bit of soil. Then use just the "core" of what comes up on your trowel to add to the sample bag.

I took samples from two gardens and you can even see the difference in the soil. The top sample is from the small garden between the patio and the house that, despite having great growing conditions, does not produce plants that thrive, leading me to believe there's something wrong in the soil. The bottom sample is from the main garden.

Label your bag and fill out the sample submission form. If you are sending more than one sample, make sure to label them in a way that makes sense to you. I used "Patio garden" and "Main garden" as well as assigning each a sample number as required on the form I sent in with them.

Speaking of forms, there will usually be one to fill out and send in with your samples, so make sure you do that. Most labs will also ask for what kind of planting is destined for the area so they can offer amendment recommendations.

Labs will have submission forms for download on their website. Make sure to fill it out and mail in with your samples.

I recently sent two soil samples in to the University of Wisconsin Soil Lab. The first is from the skinny garden between the house and the patio. This three foot strip of dirt is deep and gets full sun. It might be slightly dry because it is a little under the eaves, but I make it a point to water it. And even though sun-loving plants should thrive there, they don't. They grow, but nothing is truly happy there. Which makes me wonder if something is going on with the soi. I will probably dig out all of the dirt there and replace with with really nicely amended soil, but if there is something leaching into the soil, that should show up in a soil test.

I also sent a sample from the main garden, just because I've never tested that area.

Depending on how busy the lab is (I'm hoping I beat the spring rush), I expect to get results and a list of suggested amendments in a couple weeks. It should be interesting.

Have you ever tested your soil? What did you learn?

Does your soil pass the test?

Soil testing is one of those things you often hear you should be doing but few people do regularly. I can't tell you the number of times that our master gardener's class instructors harped on us to do soil tests. They aren't hard to do: take a sample from a few inches down, put it in a baggie, label it and mail it off to your local public university testing facility (they usually only charge about $10 and will send you a complete report with suggestions on what you should do to improve your soil).

Well, I didn't do that. With the early spring there are veggies (onions) and seeds that need to be planted very soon and I didn't want to wait for the results, so I bought a cheapie testing kit at the garden center. I doubt these are as accurate as a university analysis, but I was just looking for some general information about the health of my soil in the raised vegetable garden. It's one of those tests with a lot of little vials and some capsules that you combine with either a small bit of soil (in the case of the pH test) and distilled water or water from a settled soil and distilled water mix.

The results were interesting, although not entirely unexpected.

The first vial you see above, on the far left, was the pH in the main raised vegetable garden bed. As you can see when you compare it to the chart that came with the tests, it was fairly alkaline, probably around 7.6 or so if I had to guess (that's the disadvantage of these quickie tests, they aren't specific).

The second vial was the pH of the small raised bed I added last year outside the raised garden that I intend to grow onions in. That soil (almost all of which I added from bags last year and mixed with some homemade compost) is closer to neutral, maybe 7.2 or so.

The middle vial measures potash (or really, potassium) in the soil. I'm most perplexed by this one, because I don't really know what color that is supposed to be compared to that chart. I'm calling it medium (but it could also be very low ... hard to tell). Potassium is the "K" in the NPK numbers you see on fertilizer bags and it's necessary for plants to flower or fruit and aids with the overall health of a plant. I added some greensand, which also offers some trace minerals, to the garden to help increase this level. Greensand is a mined mineral that is rich in Glauconite.

The fourth vial is phosphorous (the P in NPK) which is important for root development and flowering. You can see that one is hovering in the low or very low territory, so I'll need to do a little something in that department as well. Phosphate and bone meal are good sources of phosphorous, as is organic matter, but you want to make sure not to overdue this one. Too much phosphorous can interfere with a plant's ability to absorb important minerals such as zinc and iron. I usually add compost to my beds in spring as soon as I can get at some, so I will probably start there before I add anything else.

And last vial, on the far right, is nitrogen, which you can see is severly lacking. This is not a surprise as soil test almost always show nitrogen is low. Nitrogen, of course, controls the growth rate and even foliage color (to a certain extent) for a plant. Manure, dried blood and urea are all good sources of nitrogen, but again you have to be careful. Too much nitrogen might give you very pretty leaves (although way too much won't) and lots of them, but it will hinder flowers and fruit and since I grow my tomatoes here, that would be no good at all! I probably won't take any steps to remedy this at this time, although I will do some light fertilizing to when the plants are growing that should help and I will plant a cover crop that will aid with the nitrogen in the soil in fall.

Do you do soil tests regularly?