Looking at basic soil test results

You’ve read it here in this blog, you’ve heard it from your neighbor, even your Aunt Bootsie told you to get a soil test for your garden.  I’ve always recommended using the soil testing lab at Michigan State University, it’s the “gold standard” of soil labs in Michigan. For most gardens a basic test will provide you with all the information you’ll need.

In past blogs I’ve described how to properly take a soil sample for testing and what to do with it once you’ve collected it, so we won’t discuss that today. Instead we’ll look at actual soil test results.

Once you’ve rounded up a bag of dirt, sent it to the lab along with your payment, the MSU soil lab will test your sample, processes the results and send you the test results either by email or by mail. That usually happens within ten days.

Let’s take a peek at an actual soil test readout I received last fall.

Results from a soil test
Results from a soil test

The first test result is the soil pH. pH describes how acid or how alkaline your soil is with “7” being neural. In this case the sample result is 7.6 which is somewhat alkaline. So right away we know we won’t have to add any lime to raise the soil pH since most garden plants grow best in a slightly acidic soil.

Next is the result for phosphorus, the “P” in NPK. The result came back at 58 ppm (parts per million) which, according to the graph is well in the optimum range.

Following P we see that is the potassium (K) is 67 ppm which we see is below optimum. Magnesium (Mg) at 202 ppm is above the optimum range.

Calcium(Ca), shown in the additional results section is 2443 ppm which helps to explain the relatively high soil pH reading since calcium will raise soil pH.

The next result is CEC (cation exchange capacity) this tells us how well the soil is able to retain soil nutrients. A reading of 14.1 tells us we can add fertilizer to this garden without having it leach out of the soil. Usually, soil types with a higher percentage of clay in their make-up have a higher CEC and therefore are inherently more fertile because of all the retained nutrients. Very sandy soils have low CEC values. It is very difficult to change the CEC of a soil. On the other hand, we can easily raise the NPK values by simply adding fertilizer.

Those cations (positive-charged ions) that are being described in the CEC reading are mostly K, Mg and Ca. There is a section in the readout providing the percentage of each of those. Phosphorus is not listed there because it exists in the soil as negatively charged anion (PO4 3-).

Nitrogen (N) is not tested for at MSU because soil nitrogen levels change with the temperature and other variables so you would never get an accurate reading.

We don’t have room here to discuss the soil science behind the results. Fortunately, the soil lab boils it all down to some simple recommendations at the bottom of the readout.

The nutrient needs are listed as actual pounds of each element per 1000 square feet. Since fertilizer is not sold as pure nitrogen, phosphorus or potassium, the precise amount of any type of fertilizer must be mathematically calculated. Back in the olden days when I was an MSU Extension Agent and the results were printed with a dot-matrix printer, I made those calculations by hand on hundreds of test results. Nowadays MSU has an online calculator that you can use to figure out how many pounds of fertilizer you would need to apply.

With the planting season rapidly approaching,I suggest you get your soil sample to the lab ASAP. Much like your income tax return; the sooner you send it in the sooner you’ll see your results.

Bob

 

 

 

Don’t till wet soil

Tilling a garden at the wrong time can be damaging for certain types of soil. That is why it’s good to know when to till. Tilling at the wrong time can be disastrous for a garden.

Gardeners make gardens in all types of soil: sand, loam, clay or, more often, a combination of two or more of these types. Short of hauling in new topsoil, there is nothing you can do to change soil type. Adding compost will vastly improve a soil’s ability to sustain plant growth but will not change the soil type.

Soil structure is different than soil type. Soil type refers to the size of the soil particles and the percentage of the different particles. Sandy soils have the largest particles while clay has the smallest, silt falls somewhere in between.

Soil structure refers to the arrangement of the sand, silt and clay particles in the soil. In soils with good structure , the soil particles are clumped together. That gives adequate space between the particles allowing water and air movement into the soil.  That provides the ideal environment for plant growth.

Tilling while the soil is too wet can destroy soil structure making it difficult for plant roots to grow.

Sandy soils are the most forgiving soil type. In a garden setting, sandy soils can be quite wet and still be tilled without doing much harm to the soil structure. On the other hand, loam or clay type soils are much more susceptible to soil structure damage caused by tilling wet soil.

There’s a simple test you can do right in the garden to help you decide when it’s time to till your individual garden. Scoop up a handful of soil and roll it into a ball. Lightly poke it with your finger. If it falls apart easily, it’s OK to till. If the ball holds together it is too wet to till. Let the garden dry out and try the test again another day.

Roll a handful of soil into a ball.
Roll a handful of soil into a ball.

This time of year, a good rain or strong thunderstorm can dump enough water onto a garden to set back your tilling plans a day or two so always check your soil moisture first.

Bob

Avoid damping off disease in seedlings by using boiling water

Growing your own transplants from seeds is a very satisfying experience and can save you money too. However it is not without it’s problems. Just about every gardener who has started plants from seed has a story to tell of watching a crop of seedlings just starting to make good growth then all of a sudden the plants shrivel at the soil line, fall over and finally die.

That is a symptom of a condition known as “damping off”. It also kills newly sprouting seeds under the soil giving the impression of a low germination percentage. The gardener gets the wrong impression that he’s planted a batch of bad seed when in reality it’s damping off.

Damping off is most commonly caused by a soil based fungus called Phythium, but Rhyzoctonia and other species of fungi can cause similar problems. Whatever the case, it is not curable.

It’s an insidious disorder. The seedlings can look sturdy and strong then suddenly,bam! overnight an entire tray of seedlings will be lost.

Most of the time you can avoid damping off by purchasing a fresh bag of sterilized soil-less seed starting mix. Sometimes however, even a new bag of starting mix can harbor the fungus, although that is pretty rare.

When Pythium shows up, it’s probably the gardener who contaminated the mix by using dirty tools, pots, or even the potting bench. All tools and containers need to be scrubbed clean with a detergent. To be doubly sure, the items can be dipped into a 10 percent solution of household bleach.

Although all plants can be infected, some species of plants are more susceptible to damping off than others. For example petunias are prone to the infection.

Pour the boiling water evenly over the whole surface.
Pour the boiling water evenly over the whole surface.

Whenever I start a batch of expensive or hard to find seeds and don’t want to take any chances of losing those precious seedlings, I take the extra step of re-sterilizing the starting mix. Some might say I’m being extra cautious but sometimes seeds are irreplaceable and need all the protection we can give them.

For small amounts of soil, I pour boiling water through a pot of starting mix — then go back and do two additional pours. If you decide to try it yourself, be sure to place the pot in a spot where the water can drain through easily. I like to do this outside on a wire rack rather than in the sink.

This boiling water method has been used by gardeners for a long time and has shown to be pretty effective. Since the entire volume of the soil mix will not reach 212 degrees Fahrenheit — the temperature at which it would be considered sterile — this could be considered more of a pasteurization method rather than actual sterilization technique.

Bob

Too much rain causes waterlogged garden soil

Gardeners in our area are having to deal with unusual amounts of water in their gardens. The amount of water in the soil is more like what we would see in early spring after the snow melt rather than late June or early July.

Driving around I see standing water all over our area with no place to go. Soils in many places are waterlogged which means big trouble for plants.

Most plants are able to cope with a day or two of flooding but after that, complications start to set in. The biggest problem is a lack of oxygen in the soil. Plant roots need oxygen to function.

All types of soil contain air spaces between soil particles. Fine textured soils with a lot of clay, have very small air spaces while sandy soils have large air spaces. This is very important because plant roots need access to soil air, they can’t efficiently use the oxygen dissolved in water.  When we have too much rain, these air spaces fill with water. Once that happens, the plant roots begin to drown and eventually die.

A water damaged plant, curiously enough, shows symptoms exactly like a plant that has been growing in a drought. In the case of a drought, there is not enough water for the roots to absorb so the upper part of the plant wilts. With a waterlogged plant, the upper part of the plant also wilts because can’t the roots have stopped working so no water gets moved into the upper parts of the plant.

After a the soil returns to normal, plants need to be watered more often because they have fewer roots. Often, if the damage is not too bad, the plant will recover by growing more roots to replace the ones lost by drowning. If it the damage is too great, the plant will be stunted and never be able to live up to its potential.

Raised beds are helpful in low lying areas.
Raised beds are helpful in low lying areas.

Another problem, especially with a vegetable garden, is the potential for contamination. In urban or suburban neighborhoods where all sorts of properties are nearby, there is the potential for flood waters to carry contaminants like bacteria or chemicals. Think of that dog kennel down the street or that parking lot with runoff water carrying motor oil and other debris.

You may want to think twice about eating vegetables exposed to contaminated flood water.

Bob

Tilling when soil is too wet will cause problems

Tilling the garden is a spring ritual we look forward to all winter. And after our cool, slow warm-up this spring, many of us will be tempted to get out there and till on the first warm day.

Be careful though, it is possible to till too early. Tilling when there is too much moisture in the soil will cause it to form large clumps, ruining the soil structure.

I did that one time early on in my gardening career. Exposure to rain and winter freezing and thawing will eventually break down those clumps. But in my case, after two years the soil was still lumpy.

A simple squeeze test will help you decide when your soil is dry enough to till.
A simple squeeze test will help you decide when your soil is dry enough to till.

To help you decide when to till, use this simple test: scoop up a handful of soil and compress it tightly, like you’re making a snowball. Poke the soil ball with your finger. If it crumbles apart, then it is in good enough shape to till. If it stays in a ball, then it is still too wet to till.

Check each day until it passes the ball-of-soil test.

Bob

November is a Good Time to Add Lime

The weather people are predicting a string of nice days through the weekend and into next week.  Many of us will looking for things to do out in the yard and garden.

Because November is the ideal time to apply lime,  this weekend would be a good time to check the pH of your garden soil. pH is a measure of acidity or alkalinity of something, in this case, garden soil.  If you have been fertilizing your garden regularly for several years in a row, the chances are your soil may need lime.

Lime is a calcium-based soil amendment that farmers and gardeners use to sweeten garden soil — raise the soil pH.

It’s not a good idea to just guess if your soil pH is low, your soil has to be tested. Fortunately, this is one test you can do yourself with a pH test kit from a garden center. These kits are pretty accurate. Just make sure you buy a fresh test kit because the test-chemicals will get old over time and produce an inaccurate reading.

There are several different types of lime and each type has a different application rate.  Don’t worry though, all lime containers have application instructions printed on them. The amounts are usually given in pounds per 100 square feet or 1,000 square feet depending on the size of the bag.

In many cases, a five pound bag of lime will be enough to treat 100 square feet of garden soil.

Keep in mind, that sandy soils need liming more frequently than loam or clay soils.

Lawns too, will benefit from a fall application of lime if the soil pH tests low.

So, there’s your excuse to head out to the garden center, pick up some supplies and get some productive work done in your garden.

Bob

Test Soil pH Before Applying Lime

Fall is the best time of year to add lime to your garden soil. This gives the lime plenty of time to react with the soil chemistry and do its job raising the pH of the soil.  The next best time to apply lime is right now, in early spring. There are several weeks to go until the gardening season is in full swing and any lime applied now will still have some time to react.

Some gardeners add lime to their gardens quite regularly without really knowing if the soil needs it or not. If you ask why often the answer is,  “we always add lime”.

Lime is a generic term for different types of calcium products. It is used to sweeten soils or raise soil pH.

Adding lime without testing the soil first is setting you up for problems in the future. Too much lime will cause such a rise in soil pH that some nutrients in the soil will no longer be available to your plants.

Lime induced chlorosis is one typical problem we see. In this case the leaves of the garden plants begin to turn yellow due to lack of iron. Iron is needed by plants and is readily available in low pH or sour soils. As the pH rises, less and less iron is available for the plant to use until a point is reached where symptoms start to show up.

A sample of your garden soil can be tested by a soils lab.  Soil pH is routinely tested along with critical soil minerals.  The most reliable tests are available through the County Extension Office.

At the very least do your garden a favor,  pick up a soil pH test kit from the garden center and test the pH yourself. Most of the pH tests are fine for home garden use.

Bob