Thanks to all the folks who warned about herbicide and other contaminants in the horse feed. I was unaware of that.

Also around here in NE TN, we can get a dumpload of manure for $50.

From:http://www.growyourown.info/page164.html

1. Take small samples from various parts of your manure heap, mix them together in a pot and then combine them with the same quantity of your soil.
2. Put the mixture into a 15 cm pot or similar and plant up with broad beans seeds. This quick growing broad leaved crop is particularly and obviously susceptible to aminopyralid contamination.
3. Plant up another 15 cm pot of your garden soil with broad beans at the same time as a control. Do not stand the pots on the same tray, otherwise the aminopyralid will contaminate the control pot.
4. Place the pots in a sheltered position, such as a cloche, cold frame or greenhouse to get quick growth of the beans, especially if testing in the Autumn or Spring.
5. Compare the leaves and growth of the test pot and the control pot. If the leaves of the growing seedlings become distorted and unnatural, as shown in the photo on the right, then assume aminopyralid contamination, and do not add the manure to your soil.

Also try:

www.motherearthnews.com/.../killer-compost-herbicide-contamination-zl0z1211zkin....