Question: Is it safe to use hay and manure in my vegetable garden?

NO!  That’s the short answer I’ve finally settled on with all the calls and plant samples our office has had to troubleshoot from vegetable gardens in recent weeks.  Please help tell your friends and neighbors they’re probably better off not using hay or manure in their gardens and here’s why:

Tomato leaves injured by phenoxy herbicides

Twenty years ago, manure was a great soil amendment to add to your garden and was considered a good source of natural “organic” nutrients as an alternative to synthetic fertilizers.  However, today it is nearly impossible to find a manure source that doesn’t contain herbicide residues, which ironically defeats the purpose of trying to be an organic gardener. 

Most folks don’t give much thought about where their manure is coming from, aside from the obvious.  However, the vast majority of farmer’s spray their hayfields and pastures with herbicides for broadleaf weed control.  Today’s hay customers expect weed-free sources of hay for their animals and farmer’s must meet the demand of their customers.  Herbicides that are used today are safe as far as having low toxicity to humans and animals.  In fact, many of these herbicides can be sprayed one day and grazed the next by livestock. 

The problem is that many of the herbicides used today also have long-lasting residual activity.  In fact, some commonly used products are known to last as long as 8 to 12 months in the soil.  Herbicide residues also remain active on forage hay fed to livestock and grass clippings from lawns that are sprayed.  If you spray your lawn for weeds, don’t put your grass clippings in your garden or compost bin either.  These herbicides are very good at what they do: kill broadleaf weeds without killing the grass.  Unfortunately, these products don’t know the difference between a weed, a flower, a tomato plant, or any other vegetable in your garden.

The type of manure used in your garden doesn’t matter either.  Whether the manure comes from horses, cattle, alpacas, goats, or other livestock, there’s a chance that they could have been exposed to an herbicide.  Even if the livestock owner doesn’t spray his pastures, hay that is purchased to feed their animals could have been sprayed.  More often than not, customers who buy high quality hay for their animals want it to be as weed-free as possible.  You can assume that any hay that is mostly weed-free has been treated with an herbicide.  About the only forage hay that will not have been sprayed is alfalfa, since most broadleaf herbicides cannot be sprayed without damaging the alfalfa too. 

If livestock owners only feed alfalfa hay to their animals and don’t spray their pastures, then you could use the manure in your garden.  However, most livestock owners also feed grass hays such as fescue, bermudagrass, and orchard grass that are likely sprayed for weeds.  However, it is your responsibility to ask the livestock owner if they spray their fields and what type of hay they feed their animals.  Otherwise, you’re better off assuming that all hay is likely to have been sprayed with an herbicide and the resulting manure will cause damage to your garden!

If you’ve already incorporated manures or hay mulches into your garden, watch your vegetables very closely for unusual symptoms.  Tomatoes are one of the most sensitive to herbicide damage and are often the first indicator of a problem.  You can expect tomatoes to have extreme leaf curling and twisting of the stems if damaged.  Usually, the newest growth on the plant is the first to show these symptoms.  If you are unsure, you may submit a leaf sample to the County Extension office to rule out any other insect or disease problems.

Paul Pugliese is the Extension Coordinator and Agriculture & Natural Resources Agent for Bartow County Cooperative Extension, a partnership of The University of Georgia, The U.S. Department of Agriculture, and Bartow County.  (770) 387-5142.  For more information and free farm, lawn, or garden publications, visit our local website at .