[Market-farming] organic compost/humus

road's end farm organic101 at linkny.com
Mon Oct 1 19:04:47 EDT 2007


On Oct 1, 2007, at 12:26 PM, David Guthrie wrote:

> i've used the bagged compost and humus from wal-mart and related 
> stores and wondered if there might be heavy metals or other 
> undesirables in the mix...
>  
> anyone have an idea?
>  
I would be suspicious of that as well. I think some sewage sludge 
materials are still on the market, and they may well have such 
problems; as might any compost or topsoil if the producers of it aren't 
careful about possible contamination of their sources. You could try 
asking the store and/or the company producing the stuff for a complete 
analysis, including heavy metal levels; I don't know whether you'll be 
able to get one, or whether the material in the specific bag you've got 
is likely to be the same as the material they ran the analysis on, as 
their ingredient sources may vary. If you can't get such an analysis at 
all, I'd be very suspicious; the store might not have it, but the 
manufacturer ought to.

Most pesticides don't survive the composting process, but some do; for 
instance, the herbicide clopyralid can survive composting and has been 
known to cause problems for crops that the compost was applied to. Your 
extension agency might be able to tell you what could be a problem, and 
you could ask for test results for those too; of course, you'd need to 
know where the stuff originally came from to find out what might be in 
use there. They could probably also run some basic tests on the stuff 
for you for not too much money, at least for lead and maybe another 
couple of the most likely problems.

There are bagged composts etc. acceptable for organic certification, 
and those should be OK; but they're often hard to find. Watch out for 
labels that are using the word "organic" just in the sense of "organic 
matter"; that doesn't necessarily mean that they're acceptable. The 
brand I use says "Approved for organic crop production". I also have to 
check specific brands with my certifier; while those not certified of 
course don't have to do that, an organic certification agency operating 
in your area might be a good source of info for approvable brands.

-- Rivka; Finger Lakes NY, Zone 5 mostly
Fresh-market organic produce, small scale
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