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Is fertilizer dangerous to horses?

From: Steven

Dear Jessica, my wife and son and I live on a small farm in Ohio. It's a house and barn and two little pastures that used to be part of a big cattle farm. We were happy to find it. It is a beautiful place and we enjoy having our horses here with us. This year is the first time our pastures are beginning to look a little thin and weedy. We have been here three years and haven't done anything to them except put up a different kind of fencing for our horses, so I guess it's time for some "pasture improvement".

My question is about fertilizers. I want to use some in our pastures and on the grass areas outside the pastures. My wife is worried that this could poison our horses. I called the extension agent and he said fertilizer wouldn't bother the horses as long as we took them out of the pastures first. He said we would need to wait for a good rain before we put the horses back out in the pastures after fertilizing. I thought I understood this, but I just realized that I don't really know why this is so important. If the fertilizer is bad for horses, why would it be used for pastures that horses eat? Whether it rains or not, won't the fertilizer go into the ground and then come up in the pasture grass, so the horses would end up eating it anyway when they graze? And if it isn't bad for horses, why do we have to wait for rain before putting them back into the pasture? We don't want to hurt our horses, but we want to make our pastures green again. Thank you, Steven

Hi Steven! You seem like a man who likes to know the reasons for things - good for you. Actually your extension agent gave you sensible advice, he just didn't do quite enough explaining.

Read the directions on your fertilizer bags/containers, and use the products in accordance with the instructions and suggestions (and warnings) listed. Yes, the fertilizer WILL eventually go into the ground, and that's exactly what you want it to do. Rain will dissolve it and carry it into the ground. That's all good.

There is a very good reason for taking your horses off the pastures and keeping them off the pastures until you've had at least one inch of rain, or the equivalent amount of water if you happen to be irrigating the pastures. (I realize that you probably aren't doing this, since you're in Ohio, but that information might help someone with a farm in some dryer part of the country.) The reason is that fertilizers (trust me on this, don't try to taste yours) are made up of SALTS (e.g., potassium chloride, ammonium sulfate, potassium sulfate, ammonium nitrate).

You know how much horses enjoy salt, and if you've had horses for a long time, you've probably seen more than one horse develop a real craving for salt and consume an entire one-pound salt block in a day or two. With a salt block designed for horses, one that's made up of sodium chloride, possibly with other minerals added, that's not going to cause a health crisis. But if let your horses go back into the pastures before there's been enough rain to dissolve the the fertilizer and carry it into the ground, the horses may seek out and consume the fertilizer itself, and suffer the potentially fatal consequences. Nitrates are of particular concern.

Track your weather carefully, and try to spread your fertilizer on your pastures and other grassy areas just before a day or a series of days when rain is predicted. Your horses won't particularly enjoy being put into a drylot (or mudlot!) for a day or three days or a week (however long it takes before there's enough rain to get the job done), but that's just too bad. Let them be unhappy for a few days - they'll be SAFE, and live to enjoy their improved pastures. ;-)


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