Turf Grass Selection Pt. 7

by George Altgelt

Certain Disaster just ahead? Soil nutrients becoming toxic? For whom? “Jeeze Louise” George you make it sound like were on a runaway train about to cross the Pecos river and the bridge is out.

OK, OK, so maybe were not all about to die but the living soil that’s about to take it on the chin. So let’s talk about how this can happen. What was once a near perfect phosphorous load in the soil is rapidly becoming too much phosphorous with repeated applications of NPK fertilizer. The phosphorous “stays put” while the nitrogen soaks away or floats away as a gas. The lawn needs just nitrogen but keeps getting more phosphorous and potassium with each new application of fertilizer. This is roughly analogous to a person being fed only carbohydrates when they desperately need protein. That person is drowning in all kinds of nutrients with no way to rebuild their body into a coherent structure for a lack of protein. Proteins, incidentally, cannot be made without nitrogen. It’s the same for people, plants, and animals. This is why nitrogen is so very important in the nutrient package carried in the soil for the sake of your plants, crops, turf grass, garden, etc. This is why water held in the soil is critical and its temperature not be too warm. But what about toxic build up and disaster just ahead? Here’s how it happens.

More and more phosphorous winds up in the soil because it “stays put” really well. At a certain point the presence of phosphorous ties up micronutrients; things like, copper, manganese, molybdenum, boron, and so fourth. Trace minerals are of great importance. For example, once molybdenum falls below one part per 600 million citrus trees will not set fruit, all those flowers and no oranges. All that work and no production. However, the main drawback to trace minerals being locked up and and not taken up (not assimilated) is this: Dramatic drop in the sugar content of plant sap. To give you a quick comparison it wouls be as if you suddenly became hypoglycemic. Your blood glucose is reading 20 when it should be reading 105! You have no energy, you can barely move. The same is true for all plants, when their plant sap sugar content drops they lose their vigor. They can hardly grow or handle changes in their environment, much less extremes. This puts them under great risk to insect and fungal attacks. If your plat sap sugar content is not where it should be you will be building your house, when it drops down you find that all you can do is stay inside lying on the couch hoping the house doesn’t burn down.

All this comes from an out of balance nutrient package in the soil. These and other disasters to be averted will be the subject or our next column.

Meanwhile, Happy horticulturi’n

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