Home Gardening Horse Manure: Crappy Soil Amendment for Your Garden?

Horse Manure: Crappy Soil Amendment for Your Garden?

Horse Manure: Crappy Soil Amendment for Your Garden?

I wrote this post after an afternoon of major weeding. I would like to correct something. Horse, Cow and Chicken manures are awesome soil amendments, but should be properly composted to kill weed seeds and ready it for garden use.

Check out these links for the inside scoop and composting poop:

(original post below)

Horse Manure and Weeds Seeds Can Go Hand in Hand

weeds sprout from horse manure

Spring weeds found in my raspberry patch, courtesy of my friend Flicka

On the daily bus/ferry commute my friend Rud contends that someone will bring up the subject of manure well before we reach the West Seattle Fauntleroy dock. On an island where gardening trumps TV and horses outnumber bicycles, Rud is right; all roads lead to that which lines a stable. So when the subject arises (and it always does), Rud remains stoic, takes a side glance at his watch and simply states the time, “seven twenty-two.” We then laugh and he returns to his paper, book or conversation—a conversation which doesn’t include talking about you know what.

This year I had an epiphany; unless a stallion jumped my deer fence, horse manure had no place in my garden. After spending years adding horse manure as a soil amendment to my upper vegetable garden and raspberry patches, a simple observation showed me the error of my ways. Horse manure comes with millions of weed seeds.

I created a large vegetable garden on the sunny frontage of my property, a place once ruled by scotch broom, blackberry brambles and weeds—lots of weeds. After bushwhacking and mowing back the brush, I took the tractor to the area and tilled it several times over a period of a couple spring months.

It’s now August and the weeds are minimal, except one area, the spot where I added one load of ‘composted’ horse manure. Within a month, that corner of the garden was a consumed by weeds, just like the upper gardens and patches. The common denominator: horse manure.From that point on, compost became my soil amendment of choice. I have the pictures to prove it.

sunflowers crowded out by weeds from seeds from horse manure

Weeds to the left, sunflowers to right

for weed free corn rows and pumpkin patch don’t use manure

No horse manure added and thus; no weeds, or very few

weed free corn rows, no horse manure added

Clean rows in the cornfield makes Tom happy

What I was blogging about a year ago: How to Build a Better Berry Basket (or Bucket)


  1. “Holy Crap, Tomcat!” What is horse manure but predigested compost? I’ve read that you should not compost weeds for that very reason as well and cat poop for some reason. At the same time, now that I’ve vented, I must add that there are a couple of things that should never be discussed in polite company, religon, politics and composting. Then I will go on to say in my undisciplined, poorly punctuated comment and at the risk of sounding self-righteous, that composting needs to be hot and thorough. Thanks, I needed that.

  2. Brion you funny man, good points all! I do have friends who cover their horse manure with black plastic to super heat it and thus (and hopefully) kill weed seeds. I’ll see how that goes for them before I try it.

    Oh, in the words of Rud….”seven thirty-one.”


  3. Tom,
    Wow !! That corn seemed to thrive in the record heat. I can’t believe how much it has grown in a week. Hopefully, you’ll be eating corn on the cob by September. As for the manure, plastic bags and poop that’s a lot of work. What about the stuff in the pretty bags at the hardware store ? Doesn’t it do as well? Manure facts that I never knew.

  4. Funny you should mention it; only chicken and cow manure are offered commercially as soil amendments…and so I rest my case. 😉

    Note to self: time to secure coop and get chickens!

  5. Okay, Brion…I’ve thought about this and I have black locust saplings all over my property and around my barn and yet no cows. So uh, the ball is back in your court.

  6. Tom – I meant no disrespect my Captain. I, unlike you, have a short commute and am somewhat antisocial. Forgive me, I have no outlet for my opinions on the breakdown of organic matter by decompostition, let alone its production and/or the beneficial and appropriate uses of the result. But I know manure when I see it. The leaves and pods of the Honey locust are just a little too flavorful for grazing animals, so much so that eons ago the tree developed thorns to regulate access to its foliage. The Black Locust became …poisonous. Yes, the leaves, pods and bark. One could postulate that any cows living near your farm probably died off long before your stewardship. In addition, cows are notoriously bad swimmers so I’m sure not many could have made it across from the main land. But I digress, The pods unlike the that of the Honey Locust is smaller and easily carried by the wind. Could this account for the distribution of your Locust saplings? Be careful before selecting chickens as your source of fertilizer.

  7. Drat, I thought you’d cave. Okay how about this smoking gun. While I’ve found countless rusty horseshoes on the property, nary a cow bell, steer horn, or milking pail has been unearthed. A-hah, there’s my smoking gun (weak, but my smoking gun nonetheless).

  8. One more thing, if you still want to use horse manure, the University of Colorado extension service points out that, “Horse manure is legendary in its potential to introduce a major weed seed problem into a garden. Composting the manure before application may kill the weed seeds if the pile heats to above 145 degrees F and the pile is turned to heat process the entire product.”

  9. Tom – Cow pies are your best bet. I’m just saying that all manure will have some residual seeds. Even birds. That is, of course, if you don’t subscribe to the Chinese method… you may not want to leave your coffee cup out there anymore . One solution is to amend soil in the fall and then just about anything will do. How’s the weather been out there anyway…

  10. So happy to have my little chickens. I just have to make sure it gets a good rest and a tumble with the rest of the pile before it gets into the garden.

  11. So true June, I loved having chickens contribute to compost pile, that is until the racoons descended with armored tanks pillaging my coop. I am currently laying land mines and barbed wire to keep the racoons at bay. When I succeed in the effort, I share reintroduce my feather friends to a more secure home (as if a moat, and gun turret weren’t enough).

  12. Clearly you do not know what you are talking about. You say the horse manure was composted but did you confirm it reached proper temperature to kill the seeds? NO! That is why the seeds survived. Just because horse manure is broken down does not mean that it reached proper temperature. Call it broken down not composted the next time you post instead of misleading people. Clearly you just delete comments people write that are not agreeing with you, it is sad. I studied horticulture and your post is so far from scientific it is funny. Try getting horse manure, composting it properly and then trying it. Until then stop spreading ignorance! -Humboldt Grower

  13. Alex, ouch! Your comment is surprisingly harsh. Could you not have begun with I disagree and here’s why. You went from zero to sixty in a few words. First of all, no comment deletion here. I welcome all non-offensive comments, even the less gracious ones (as you can see). 😉

    Now to the issue at hand. Yes you are right, horse manure is awesome, and I use it regularly now and will update shortly saying such. Yes, I had used some manure that had not been composted properly and it had every seed in King County in it.

    So Alex, truce, you were right and I was wrong: horse manure needs to be properly composted to kill weed seeds. Good growing to you in Northern California.

  14. Hello, I found your blog looking for pinhead oat recipes and am enjoying everything else too! (I have no problem talking about poop and food in one comment).

    Just wanted to add a little concern of mine regarding horse manure in a vegetable garden. Namely, Strongid. Many horse owners use daily or monthly wormer in their horses and what goes in one end, comes out the other. I do still sometimes use it to amend or start new perennial beds, but I keep it away from my food.

  15. You’re welcome. Pfizer says it is safe to use the composted manure but their reasoning is that sunlight breaks down the chemical pyrantel. My compost pile doesn’t get a lot of sunlight and certainly not all the way through. I have never been able to get my questions about its safety in the environment answered to my satisfaction.

  16. I agree that horse manure has less weeds if it is composted. It helps to use a mulch (pine needles) as well to reduce weeds. I have found that composting also helps reduce the nitrogen level of green manure so plants aren’t burnt up. I put 3 five gallon buckets in my radio flyer wagon and walk around the pastures shoveling up horse apples for my compost pile. My neighbors think I’m crazy. My horses know I’m crazy. Oh well, life is too short to care!!
    Happy Composting


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