A Cautionary Tale

Photo by Peggy McDonald

A soil test last fall revealed that some of the VegHead Garden’s beds are quite high in copper, particularly those where we have added a lot of commercial garden mix created from animal manure.

While composting has been shown to reduce the bioavailability of copper and other heavy metals, they can still accumulate in the soil.   This can affect germination rates and plant growth.  Copper also has antimicrobial qualities which can reduce the activity of essential microorganisms in the soil. 

It has long been known that composted animal manure tends to be high in copper because of copper that is added to animal feed for domestic animals to help furnish minerals for animal nutritional needs and because of its antimicrobial characteristics.  This includes mushroom compost, which is usually created from animal manure, blood meal and grain straw.

We had been using bulk garden mix from local suppliers, and following the soil test, we were looking for alternative products to top up our garden beds and provide nutrients to our crops.  When extension agent Mark Tancig contacted Black Kow to see what the copper content was in their commercial product, they confirmed that it was also high in copper. They graciously donated many bags of their 100% cow manure compost to us, which we will use with the addition of an equal amount of garden soil, potting mix, or our own compost, which is free of manure.  This will dilute the copper concentration to which the plants are exposed as well as any other heavy metal residue   

Soil tests are recommended to not only test for copper, but  potassium and phosphorus as well as soil pH   Proper levels of all these elements are essential for your garden to thrive, Soil test kits can be obtained from the Leon County Extension office on Paul Russell Road.