July 17 - A reader asks:

"With the extensive use of antibiotics, anthelmintics, and hormones in cattle and other livestock today, is there not a risk that these contaminants would be present in blood meal?"

Questions similar to this one come in pretty often. People also ask about chemical pesticides that may have been spread on the crops used to produce the seed meals I advocate for fertilizer.

If you're concerned about the uptake of these chemicals by your vegetables, then you likely don't need to worry. These chemical molecules are quite large, so they're not going to be absorbed along with water - nothing larger than a water molecule will make it through the root cells' membrane. The mechanisms used to pull in nutrients are quite specific to those particular atoms/ions, so that particular doorway is also shut.

Surface contamination may be a bigger concern to you. My personal opinion is that these chemicals are not likely to survive long out in the open, what with the exposure to ultraviolet light, water, soil acids, and such; but I have not done the in-depth research that would allow me to state that as a fact. I do think it is a good practice to scrub your root veggies with a brush before using them, for various reasons.

It is possible that some of these compounds could have an adverse effect - at least in the short term - on the creatures living in your soil. I don't know that this has been studied. You can ameliorate this by using certified organic meals, but they can be harder to find and are probably more expensive.

To be honest, I am more concerned with the impact these chemicals may have on us directly when we consume meat, milk, cheese, and other animal-based products. I would like to see a major overhaul in how our beef, pork, and poultry farms are managed. Unfortunately the majority of people in the US and elsewhere are so driven by absolute price that I don't have much faith in the system changing substantially in the near term. My family buys milk products and eggs from a dairy (Smith Brothers Farm) that, while not organic, pledges to not use hormones and antibiotics when raising its animals (they don't produce their own cheese, unfortunately). Finding meat that has been raised with similar care is a hit-or-miss proposition, though.

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This page was last updated November 18, 2013