A friend of mine recently tried straw bale gardening and had a dismal failure. This caused him to do a bit of research and he found an article in the current (January/February 2016) issue of Backwoods Home magazine, on a product called Grazon, one of many aminopyralid herbicides used on hay and straw field to kill broadleaf weeds. That may explain his failure.
Grazon or other Aminopyralid-containing herbicides are sprayed on pastures and fields of straw and hay because they only kill plants such as horse nettle, pigweed and blackberries not the feed grass. After it is applied, the cows, horses and other animals graze on the grass, ingesting the herbicide which passes through their systems and into their manure.
Herbicides containing Aminopyralid (sold as Milestone, Milestone VM, Milestone VM Plus, Chaparral, CleanWave, ForeFront, GrazonNext, Opensight and PasturAll) have been available since 2005 and were marketed to horse and cattle owners to control perennial weeds. They are now in common use in the US in straw and hay fields. There is an article in Mother Earth News that gives quite a bit of information on these herbicides.
The articles in both magazines pointed out that the use of these herbicides has resulted in the destruction of many home gardens in both Great Britain and the United States. Some of you may have been affected and not have known what caused your garden to die.
The chemical companies have been protected to some degree by the warning they have placed on the label. “Do not compost or mulch plants with grass or hay from treated areas, or with manure from animals that have foraged on treated areas”.
I talked to a friend of mine who is in the weed control business and he provided me with the following information. You can’t feed dairy cattle on grass, hay or straw that has been treated with this herbicides. You can feed horses and beef cattle. He says that if he is going to use straw in his garden, he lets it sit for a least a year, until it starts to rot and the chemicals will break down. The same thing with manure, it will need to compost for at least a year.
He said that if you are using any pesticides or herbicides be sure to read the warning labels and closely follow their instructions. My friend said manure purchased through large chain stores and garden supplies should be ok, but if you are getting it from other sources ask questions.