According to the North Carolina Cooperative Extension, many home gardeners have reported damage to their vegetable and flower crops after applying purchased compost, hay or manure to their soil. Reported symptoms are death of young plants; twisted, cupped, and elongated leaves; misshapen fruit; and reduced yields.
There is a class of herbicides called pyridine carboxylic acids that is used to control a wide variety of broad-leaf weeds and is designed to safely pass through the digestive tract of livestock and horses. But here is the thing: these chemicals, namely picloram, clopyralid, and aminopyralid, can remain active in manure, hay or grasses for long periods of time; even after being composted. While currently deemed safe for human consumption, these materials are then used to commercially produce compost that could potentially end up in your yard and on your family’s vegetables causing damage!
Make your own compost so that you have control of your garden so that these chemicals do not get into your soil! Or if you need to purchase compost in bulk make darn sure that the supplier can guarantee that no chemicals were used on the materials that were used to make that compost.