This summer, some gardeners in Asheville thought they had plant damage from some locally obtained composted manure, so we ran a test. You can get the full story on the situation, the test, and earlier results by reading the three previous posts on this blog from July 9, July 26, and July 29, 2010. Or just click on "herbicide carryover" in the labels section on the right sidebar of this blog.
Here are the final results from that study. These plants have been grown for seven weeks in a mixture of the composted manure with standard potting mix, in the potting mix with the suspected hay on top, and in just our potting mix. Note, the damage did not become apparent until the plants had been growing for five weeks! Also keep in mind that these plants have now been growing in these little pots for seven weeks. They are totally root bound. So even the control plants (in straight potting media) don't look great.