Iron from brake shoes won't help

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Question: Can I use filings from resurfacing auto brake shoes and rotors to add iron to my vegetables?

Just adding iron to the soil is not enough. Actually, there is quite a bit of iron in our soils already.

But the iron in our soils and rocks is the wrong kind for plants to use, just like the iron from brake shoes. The high pH or alkalinity of our desert soils prevents the iron contained in it from becoming available to plants. As soil alkalinity or pH increases, the iron already in the soil becomes less available.

Iron exists in a plant-available ferrous form and an unavailable ferric form. Iron can shift between these two states, depending upon the alkalinity of the soil and how much air is present. Because of the high pH of our soils, most of the iron is in the ferric state, the form unavailable to plants.

In theory, you should be able to release iron from our soils if you decrease the alkalinity or lower the soil pH. One product sold locally called Ironite is based upon this principle. This doesn't always work because any lowering of the soil's alkalinity is only temporary. Sooner or later, the soil returns to its alkaline nature.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension.