Let it Grow: Improving soil may be the key to solving plant problems

How's your soil feeling?

As I was taking soil temperatures this past week, it struck me most people would find it puzzling why I might be checking the soil's temperature. Am I really trying to determine if your soil is healthy?

Well no, not really. I am checking to see when I might expect certain weed seeds, such as crabgrass, to start geminating. This can be a useful tool when controlling weeds.

Even though taking your soil's temperature does not tell me anything about its health, I do evaluate general soil health in every yard where I work. I check soil health by poking, probing, digging, feeling and smelling to check the soil's physical condition. If plant color or growth rate suggests a nutrient deficiency, I may send a sample to a lab for nutrient analysis to evaluate a soil's chemical properties. However, I am most interested in the soil's physical properties in most yards.

Soil physical properties have the largest influence on root development. If soils are loose (friable) and well aerated, plants will develop large and healthy root systems which are very efficient at taking up water and nutrients from the soil's reserve. Plants will not develop healthy root systems in soils that are compacted and poorly aerated.


Most people, landscape service providers included, automatically will assume that fertilizer will improve the soil and thus improve their lawn or other plants. Fertilizing changes nutrient levels but does not improve the soil's physical properties or build soil as some claim to do. In fact, excess nutrients can make problems worse by forcing growth when plants may have poor roots because of poor soil environment.

Customers often ask how to tell if their soil is in good condition. The easiest method is to take a long thin screwdriver, or other probe, and push it into the ground. If it pushes in easy you have good friable soil. If it pushes in hard you probably have some level of compaction that limits your landscape's health.

So this begs the question: Can soil physical properties be improved? Fortunately, the answer is yes, but unfortunately, it can be expensive, so soil improvement generally is done on a selective basis to improve problem areas.

Adding organic matter to the soil is the only way to effectively improve soil condition. The simplest and most cost effective way is to leave grass clippings on lawns and to shred leaves to filter back into lawns or use them as mulch in landscape beds. Over a time period of hundreds of years, new and improved soils will develop by simply keeping these organic resources on our own landscapes.

Now, most of us don't have hundreds of years to wait for our soils to improve. The landscape maintenance industry has developed methods of speeding up the process by applying organic mulches and composts. The use of wood mulches on landscape beds has become a common practice in our region. Commercial application of compost is just beginning to be more common, but the benefits are well documented from areas where this practice is common.

Compost can be spread over the surface of lawns and raked into the grass. If done in early fall, it can be applied to a depth of about a half an inch. It will look terrible for a while, but the grass will come through and be better off for it in the end.

Around trees, compost and mulch on the surface will improve tree health considerably. In situations with very poor soil, compost can be incorporated into existing soil with an air spade. This is basically a large air nozzle that is run off a big compressor.

I am not suggesting that homeowners start spending a lot of money on spreading compost over their entire landscape, but it is a practice that should be given real consideration for problem areas in yards. Research has consistently shown that adding organic matter to poor soils greatly enhances the growth of all landscape plants.

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