Turf Grass Selection Pt. 6

By George Altgelt

So, how tall should turf grass be? That’s what we were looking at the last time. With turf grass our range of choices are limited to the settings on the lawn mower. Even so, what you choose will have an enormous impact on the vitality and productivity of your lawn. Taller grasses mean cooler soil, greater water retention and better soil ecology. This was the idea put forth in my last column, along with indications this will save you money. So what’s the mechanism here?

Let’s start with the typical mistake (or ploy) on the part of the lawn care company (guy with a lawnmower) of lowering the lawn mower in the summer months because the grass is not growing very fast. Possibly it hasn’t grown at all since the last time it was cut. “I’ve got to make it look like I did something, I’ve got to justify my bill” is the usual motive behind this high crime. More light is then absorbed by the soil, which turns to heat. Hot soil holds much less water. Now, water is the medium for absorbing nitrogen that is released from the decomposition of proteins from all those grass clippings that hopefully know one is bagging up. Of course there is much more to those clippings (phosphorous, potassium, macro and micro nutrients, and cabohydrate energy for microbial life etc.), but nitrogen (as a gas or as nitrates and nitrites) must be in the presence of adequate water to be dissolves and held long enough to be absorbed by the plant roots.

The key word here is “held.” Some soils may have barely adequate to fair water holding capacity, but take away the shade by mowing the grass too short and it can’t hold nitrogen long enough to recycle it. Nitrogen just floats off as a gas. Then your nutrient package goes out of balance because the other major plant foods are minerals. Those minerals can range from adequate to abundant but the grass won’t grow because it needs nitrogen. The lawnmower guy figures it is time to fertilize, he gets you to spring for it and comes back with some high number fertilizer like 24-10-10. The 24 represents high nitrogen whereas 10-10 represents high phosphorous and potassium levels. In this fertilizer the nitrogen is a water soluble salt, it sinks downward through the soil and winds up in the creek or aquifer. The other nutrients don’t leech downward so easily and they build up to toxic levels. This further imbalances the nutrient load in the soil. What certain disaster lie ahead? You won’t want to miss next weeks column.

Meanwhile, Happy Landscaping

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