Organic Fertilizer and Heavy Metals

Like many stories, this one begins on a lovely spring day. It was just dry enough today in western Washington to mow the lawn for the first time. If I did not get it today, it would have surely meant the Stihl trimmer would have to put the first cut on it after another week of rain. So, avoiding that, I was grateful for the opportunity to get it now with the mower.

One thing led to another, and next thing you know I was hearing from a friend about how the new garden at the White House in the other Washington had the list-serve all a flutter this morning. Turns out there was a fair bit of concern about what sorts of lawn chemicals had likely been used in the recent past on that stretch of grass, and how it must be enough to undermine the claim of organic.

Now, before I continue, I want to share with you some of my background. It was about 1992 when I first stepped foot in the door of Black Lake Organic. This is a small gardening shop on the shores of beautiful Black Lake outside of Olympia, WA. At the time this was quite the rustic operation. The fellow who ran the shop, and owned it, and built it, and would soon employ me for six years and be my friend until this day, is a man by the name of Gary Kline. Now Gary was not much for bureaucracy, or the paper work that went along with it. So, the fertilizer operation at the time resembled something that would have taken place in the last century, meaning the 19th. I was quite impressed though, it was like an apothecary's shop, or the sort of place you find in the opening moments of a spooky movie, where the protagonist buys some exotic powder or the pulp of some very rare plant.

Though it may all seem very exotic, everything there could be divided into one of three classes; animal, vegetable or mineral. In all three of these classes the material was usually ground into a meal, producing for example, blood meal, alfalfa meal, and limestone flour. Well one day a customer, who also happened to work for the state, noticed that we bagged small quantities of any and all of these materials for resale in the store. We would buy in fifty pound sacks, and sell in any bulk quantity the customer wanted. Of course they informed us, we needed a special permit to do this, and part of what that permit requires is a nutrient analysis of the material, printed on a label and applied to each of these bulk packages.

You are probably familiar with NPK. Nitrogen, Phosphorous and Potassium. Three of the major plant nutrients. It was quite an undertaking to get all of the materials we used tested and registered with the state of Washington. But we undertook the task, and Gary still operates the store and sells all of the organic fertilizers there to this day.

It was 1997 that the Seattle Times published an investigative piece on heavy metals in fertilizers. All types of fertilizers were analyzed, organic and synthetic included. Yep, that’s right, there was contamination of the fertilizer with heavy metals, but it may come as a surprise to you where these contaminants turned up. Turns out, Miracle Grow was as clean as a whistle. After all, it is a synthetic creation, so it only had elements that were intended to be there in it. The organic fertilizers on the other hand, were loaded with heavy metals, cadmium and arsenic being the two most abundantly discovered.

The rock phosphate mine in Idaho that was supplying the rock used in the organic fertilizer was loaded with the metals. When the same rock was processed to make the super phosphate used in the miracle grow, the cadmium and arsenic were removed in order to increase the concentration of phosphorous. Of course, somewhere this very concentrated waste lies today. When it came to organic standards, which dictated that the rock could not be modified if the fertilizer was going to be called organic, that cadmium and arsenic was being very modestly and evenly distributed all over the country on peoples organically tended lawns and gardens.

Not long after the article in the Seattle Times, heavy metals in fertilizer fell under state regulation here in Washington. We had to submit all of our fertilizers for laboratory analysis to determine the concentration of metals in them. These totals dictated the application rate of the fertilizer, and the associated numbers were made available to the public on a website. Several products, including that Idaho rock phosphate, were too contaminated to continue to be used. Another mine, in Montana, soon came online and supplied us with a less contaminated rock phosphate.

This brings me back to my conversation this morning. Upon being told about the concern for the lawn at the White House, I informed my counterpart in the conversation that when I discuss with clients their concern for past contamination in their yard, I often reassure them by saying, 'hopefully they were not using organic fertilizer.'

Two other sources of possible contamination with heavy metals are fertilizers derived from sewage sludge, or trace element products that are really just a clever way of disposing of industrial waste while still turning a profit for the manufacturer. In the state of Washington (and possibly Oregon, California and Texas) heavy metals are regulated in fertilizer. You could also track down information on brand names and generic products at the Washington website.

A good rule of thumb that I share with clients of mine (I design and install natural/organic food producing landscapes) is; whatever you have been doing a lot of, should probably stop, and something you have not been doing could take its place. Meaning, spreading wood ash on your garden is good, until you have done it too much, which happens rather fast. If you use rock phosphate every year, stop it, you have enough phosphorous, and it lasts a very long time. If you every year apply chicken manure to your garden, stop it, you have enough nitrogen and probably way too much phosphorous. If you never eat meat, have a hamburger, it is probably just what you need.