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Post by octave1 on Mar 15, 2024 10:02:22 GMT -5
Last year's potting soil was a disaster for me. I nearly lost all of my seedlings, and since this has happened to many other gardeners, I knew that something must have been wrong about the potting soil mix. Today, as I was chatting with another local gardener--and based on what my seedlings exhibited, I think I finally found out what the offending substance contained in the mix may have been: aminopyralid." Aminopyralid (marketed as MilestoneTM, ChaparralTM, and OpensightTM ), is an auxinic growth regulator herbicide and will cause damage to sensitive broadleaf plants such as tomato, lettuce, beans and peas. Impacted plants will usually not die when exposed to low residue amounts in compost, but will produce few quality fruits or no fruits.
Aminopyralid breaks down slowly or not at all in the digestive system of a cow or in the composting process, but instead, remains with the organic matter throughout the composting cycle. Problems arise when this compost is used to amend garden soils. Concentrations as low as 1 part per billion (ppb) of aminopyralid will affect sensitive plants such as vegetables. Damage to broadleaf plants includes cupped leaves, twisted stems, distorted apical growing points, and reduced fruit set." Source: smallfarms.oregonstate.edu/smallfarms/aminopyralid-residues-compostNeedless to say, I will be very cautious about potting soil this year, and I will definitely conduct my own bioassay (as suggested by the article) before I use any kind of potting soil and commercially available compost.
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Post by september on Mar 15, 2024 11:06:45 GMT -5
octave1 , I hope all affected gardeners are writing or calling the companies that produce the seedling killing potting mixes to complain loudly! By now the producers should know enough to be doing their own testings of soil or compost additives before they go into their commercial bagged mixes. Does not make much sense to keep producing a product that kills or maims what it is supposed to grow!
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Post by Laura_in_FL on Mar 16, 2024 10:05:49 GMT -5
I had the same problem last year, octave1. Some of my tomato seedlings didn't die, but just sat there and would not grow. I kept them for months out of sheer curiosity and they just sat there in their pots as if in some sort of sci-fi "stasis." It was so strange! This year I coughed up the cash for Pro-Mix and my seedlings are happy. Any certified organic potting mix should be safe - aminopyralid and other persistent herbicides are not allowed for certified organic production. But certified organic potting mixes can be expensive. But the bio-assay is essentially free; it just takes time. It's a smart idea for any incoming potting mix or compost these days. The thing is, you have to test every bag/batch. Even within the same brand, different batches can have ingredients from different suppliers, so while one bag or batch of "Brand A" might be fine, another might not.
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Post by paulf on Mar 16, 2024 13:35:40 GMT -5
Excellent warning! Thanks. The only problem I have had was when using the really cheap off brand stuff. This year the brand name mix is doing fine. No more brand X.
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Post by octave1 on Mar 16, 2024 18:58:55 GMT -5
Any certified organic potting mix should be safe - aminopyralid and other persistent herbicides are not allowed for certified organic production. But certified organic potting mixes can be expensive. Laura_in_FL , my bad potting soil last year was organic, Miracle Gro Organic Choice potting mix to be exact. It did not seem to affect all seedlings, but tomatoes and, to a lesser degree the other nightshades, were definitely affected. I will never again buy Miracle Gro products, no matter what their claim is, and any other brand I may favor in the future is going to have to pass the bean test, period. I am actually quite wary of commercially available compost as well, since it's likely to contain composted cow manure from cows fed herbicide. According to www.ams.usda.gov/grades-standards/soil-building-manures , "Manures from conventional systems are allowed in organic production, including manure from livestock grown in confinement and from those that have been fed genetically engineered feeds." The way I see it, anything labeled "natural fertilizer" in a potting mix should raise a red flag.
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Post by Laura_in_FL on Mar 17, 2024 11:10:12 GMT -5
Oh, yikes. I didn't know that, octave1. Scratch what I said about "organic potting mixed should be safe." Test everything!
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Post by paulf on Mar 17, 2024 23:51:25 GMT -5
Two years ago I bought several bags of the Miracle-Gro Organic potting soilless mix and had zero problems. That same year we bought some local hardware brand mix and it was sand and mud and it was used to fill in a low spot in the yard. I spread some grass seed on it, but the mix turned to concrete. It was a good pothole filler and that is about all. Menards Expert Gardener is hit and miss whether it is mostly sticks and rocks or really good stuff. Schultz has been OK. Mostly I stay with Miracle-Gro in the yellow bag.
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Post by pepperhead212 on Mar 18, 2024 16:59:50 GMT -5
It was too cool to do any more of the staining of the deck, and the only thing I got done was mixing up the seedling mix. I was glad I do this, partly because I'm a cheapskate, and the plants do so well in it, but also because I've been hearing all these horrible tales about people having problems with herbicides in their potting mixes, sometimes "organic" ones of major brands. I just mix some peat, with some dry coir I had left from the hydroponics, and about 20% perlite, with a little granulated diatomaceous earth, for drainage, and about 10% worm castings - the only fertilizer I add to it. It was sort of good that it was so windy - it blew the dust away, as I mixed it up, as long as I stood on the right side! Worm castings added to the seedling mix - peat, a little coir, and the perlite, with a little granulated diatomaceous earth. by pepperhead212, on Flickr Finished seedling mix. Extra will be used for topping off SIPs. by pepperhead212, on Flickr Before using it, I'll sterilize it, by a low cook (about 200°) let it cool, then add some Bt israelensis to it, to prevent the fungus gnats.
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Post by Laura_in_FL on Mar 18, 2024 17:01:37 GMT -5
That looks like good stuff - no wonder your seedlings do well in it.
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