Before making use of ditch hay, be sure to know what, if any, herbicides were applied. It could help you avoid potential carryover in the manure of animals eating that hay and prevent damage to other crops, says Lizabeth Stahl, University of Minnesota Extension educator.
Products with the active ingredients picloram (Tordon, Grazon and Pathway), clopyralid (Stinger, Curtail and Transline), or aminopyralid (Milestone and ForeFront HL) help control broadleaf weeds in cropland, rangeland, pastures and along roadways. The chemicals pass quickly through – without significant degradation – animals fed hay treated with them. Manure and urine from those animals, however, may contain enough herbicide to injure or kill sensitive broadleaf plants, including soybeans, lentils, peas, legumes, potatoes, tomatoes or peppers.
Check with the hay supplier or a local, county or state agency to find out if the ditches in question were treated with herbicide. A bioassay is recommended or required before a broadleaf crop can be safely planted on ground that may contain picloram, clopyralid, or aminopyralid applied through manure. Refer to the pesticide label for specific restrictions and recommendations.
The article, Use Caution When Harvesting and Feeding Ditch Hay, discusses this issue in greater depth. Although the article focuses on picloram and clopyralid, aminopyralid – released after the publication was created – has potential to cause similar injury.