Can you have too much manure on your garden?

[Skydreamer]

Help, my husband had two loads (1 ton each) of organic cow manure added to our garden. It is a vegetable garden and its not doing much at all with any of the plants. The plants are started from seedsin a greenhouse, then transplanted into the garden...where they seem to be dying.
Usually the garden is flourishing this time of year. Only difference is, there is much more manure on the garden this year. Could that burn the soil and be killing the plants?

Any advice? suggestions?

Thanks,
Cat

[cynthia_h]

If this cow manure was fresh and not composted, then yes it is killing the plants from excess nitrogen burning their roots. There's also a question of pathogens which may be present in uncomposted manure (e.g., E. coli), which brings up a separate question related to food safety. There's a [url=https://www.helpfulgardener.com/forum/viewtopic.php?t=36462]current discussion[/url] here at The Helpful Gardener related to the E. coli outbreak in Germany.

If the manure was already composted, the sheer quantity of it may be overwhelming the young plants. Although you don't say how large your garden is, 2 tons = 4,000 lb. Unless we're talking about acres rather than square feet, such a quantity of manure would lead to a nutrient imbalance.

If such a windfall of manure should come your way again, it might be more helpful to the plants to spread it over the soil in the late fall so that winter rains/snow can compost it or finish composting it and drive the nutrients further into the soil, where they'll be available to plant roots in the spring. Right now, everything is right at the surface.

Cynthia H.
Sunset Zone 17, USDA Zone 9

[toxcrusadr]

The previous answer is probably it, unless it has a huge amount of straw, sawdust, wood chips etc. mixed in. I've gotten horse bedding like that before. It can actually deplete nitrogen if there is more woody stuff than manure. If it was piled up and partially composted, it may be hard to tell, but it could be nitrogen deficient.

So the main thing to find out is whether it's fresh or aged, what it looks like, and what they used as bedding.

And tell us how big your garden is!

[Skydreamer]

That's what I feared...over fertilized the garden. The garden is 25' by 75'. 1st load of the manure was composted, dry and a good mix. 2nd load was fresher, straw, lots of hooves, and quite damp.

I've always had a garden each yr, but am new to having it be totally 100% organic....and from the sounds of it, we aren't off to a good start.
Didn't help that my husband wanted to make sure we had enough fertilizer/manure added. I think we will let this yr pass, hoping the rain will help soak in down into the ground and try again next yr.

Thank you both for your advice and suggestions.

Cat Steffen

[amyb1984]

is also quite expensive isnt? I mean yes important for the garden...but man!

[toxcrusadr]

Curious about roughly how thick the layer was before tilling in...an inch, 6 inches...?

Best way to do this might be in the fall, after a frost when you're done with the garden, and let it incorporate over the winter.

If you are able to try some late crops, you can try planting something after a couple weeks and see how it does.

[Gary350]

Too much nitrogen could be killing your plants. Add a lot of saw dust, leaves, dry grass anything organic you can find and till it in the soil. It will take a month or more for that organic material to lower the nitrogen.

[toxcrusadr]

I'm thinking it will balance out by itself in couple of months. By next spring you're going to have a helluva garden...

[roostershooter]

Skydreamer, I just did the same thing. I added about 3 or 4 wheelbarrow loads of rotted manure to each 4X10 beds and planted my veggies. This ammounted to about 6-8 inches of manure. I tilled it in. Everything is dead or did not come up like the beans. The way I see it, I have to completly empty the beds, and start over with fresh topsoil. The manure I put in was supposedly 10 years old and seemed to be rotted. Anybody have any other suggestions before I do all that work again?

[SOB]

rooster, I don't see why you have to empty the beds and put in new topsoil. If there was too much hot manure it will eventually break down and the soil will be just fine.

[roostershooter]

You think that the soil will be fine for next years garden? I hope you are right and will consider that. I am not sure what another year will mean since the manure was already 10 years old, but it would sure be nice to not have to start over again. I was thinking that I needed to get the material out of the beds that ruined it in the first place.

[toxcrusadr]

I can't imagine why 10-yr old manure would do that. It seems like it should be completely, absolutely, positively broken down to ultimate humus. Any imbalance of brown vs. green would long since have been worked out one way or another by microbes. I'm not sure what the explanation is.

[roostershooter]

I do not have an explanation either, that is why I jumped out here to see if I could get an answer.

[cynthia_h]

The manure I put in was supposedly 10 years old and seemed to be rotted.

I have two thoughts on this "10-year-old, well-rotted" manure.

1) No way that it was 10 years old.

2) There's something else in it in addition to manure; perhaps herbicides? or anti-worm meds from the animals whose manure it is? This is an especially strong possibility given my belief that the manure is much "younger" than represented to you.

Cynthia H.
Sunset Zone 17, USDA Zone 9

[vermontkingdom]

Ten year horse manure should be fine. However, sometimes animals get field hay that has been treated with a particular kind of herbicide that takes a very long time to break down. This stuff might still be active enough to prevent plants from growing. You could run a simple experiment-= take a couple pots of it and plant a few pea/bean/radish seeds. If they germinate and grow, everything is fine. If not, you should get rid of it.

[roostershooter]

The manure came from sheep. We did exactly as you suggested, put some in a pot and planted tomatos. They both died. The new leaves would start and then curl up and the plant would die. The manure was mixed with potting soil. The manure was not green, no odor at all and mostly black in color. It may not have been ten years old, but it was older than several years. I think I will remove as much as I can and start over. I put in a pickup load in 5 4x10 beds. What I tried to do was make my garden much better by doing this. Instead, I ruined the garden completely.

[Alicemae]

That's so sad that you think you're doing wonderful things to and in your garden and turned out to be the opposite - I am sorry...

But, my question is this; all of my 2 year old chickens (15) were killed in one night by a mink or minks (I think cuz they've been seen around here) and I'm thinking to clean out the 8' x 10' house they lived in and dump it all in my garden before the fall tilling. It's 'ditch grass' hay and poop - no straw or wood chips.
Is that an alright idea or could there be some unknowns lurking?

Thanks for any thoughts - Alicemae

[vermontkingdom]

Chicken manure would be great by next spring. However, I would worry a bit about potential grass seeds being put into the garden in great numbers without them being hot composted. I normally compost everything but several years ago, late in the fall, I was offered and accepted a large load horse manure that went directly into my garden. It was a huge mistake because I introduced a wide variety of weed seed that I continue to battle many years later.

[Alicemae]

Chicken manure would be great by next spring. However, I would worry a bit about potential grass seeds being put into the garden in great numbers without them being hot composted. I normally compost everything but several years ago, late in the fall, I was offered and accepted a large load horse manure that went directly into my garden. It was a huge mistake because I introduced a wide variety of weed seed that I continue to battle many years later.

Thank you for the tip on chicken manure. If it's put into the garden in the fall will the seeds still germinate in the spring? Minnesota winters are brutal!

I made that same mistake with horse manure about 5 or 6 years ago and it was just recently that I was told. The vine-like weeds that grow low to the ground and spread like wild fire are called Bind Weed and next to impossible to get rid of. Apparently something in the grains given to horses are the "seeds from hell" - really! I'll never make that mistake again and I try to warn as much as possible to all gardeners - beware!!

[farmerlon]

I hope this is not what happened in you garden...
but, here's an interesting article from Mother Earth News about "killer compost"...
[url]https://www.motherearthnews.com/organic-gardening/killer-compost-zmgz11zrog.aspx[/url]

[toxcrusadr]

A pickup load of well-aged sheep manure spread over 200 sq ft should NOT have that kind of effect. I too am starting to wonder if there is something in it that is causing problems. Can you talk with the owners of the sheep and find out what they're using on any fields and pastures that supply food for the sheep? It's starting to sound like a persistent herbicide is a possibility.

[toxcrusadr]

For posterity here's the opening paragraph of the Mother Earth News article that farmerlon linked:

The aminopyralid herbicide known as Milestone, plus other related herbicides collectively known as pyralids (sold under the brands Confront, Curtail, Forefront, Hornet, Lontrel, Millenium Ultra, Reclaim, Stinger and Transline), are still surfacing unexpectedly in gardens throughout the United States, with devastating results. The EPA allows Dow and others to sell these potent weed killers to farmers, who spray them on their pastures and hayfields. When animals graze on the treated pasture or hay, the chemicals pass through the animals and persist in the manure for several years — even if the manure is processed into compost! Gardeners then use the contaminated hay or compost on their crops, bringing a slow death to carrots, lettuces, potatoes, beets, spinach, tomatoes and legumes, including (but not limited to) beans and peas.

[roostershooter]

Tox, I contacted the fellow who I got the manure from and told him what had happened to my garden. He immediately started to accuse me of wanting to have him pay for the lack of vegetables this year and that his mother used the manure for years without any trouble. I told him I put the pickup load on the beds and he said that I put way too much on. Anyway, the conversation did not go much further and consisted of two pretty mad people. Never got around to asking him about herbicides or pesticides. I am thinking before I plant next spring, I will do a basic soil nutrient test, at least for N.

[FlowerPowerGirl]

I never had a problem with compost. I always use my own homemade compost though.

[toxcrusadr]

Sorry to hear the conversation didn't go well, rooster.

If you can't grow a tomato in a pot by mixing it with potting soil, it sure sounds like something is wrong with this compost. Lots of people will say they've had plants sprout right in their compost piles that grow better than anything in the garden. Manure, if fully composted, should be a lot like any other compost. The composting process is the great equalizer. I wonder if the guy's mom didn't have problems because she used so little of it. We might never know. A soil test is a good idea, in fact you might even think about doing it this fall before it gets real cold.

[roostershooter]

I thought I would bump this up with the results from the garden this year. I tilled the beds twice last fall and twice again this spring before planting. The vegetable plants were put in two weeks ago and everything is doing great. The beans are coming up and not dying, a huge improvement from last year. I think the problem is that I put too much in and it was too hot for the plants. The next time I add manure to the beds it will be just a top dressing, a minimal amount.

[toxcrusadr]

Thanks for checking in with the results. Glad your garden did a lot better this year!

It could be just an overwhelming amount of organic matter that shocked the soil system one way or another. The good news is you won't *need* those kinds of amounts to maintain now that your soil is so delicious.

[rot]

..
Thanks for the update.
..

[estorms]

Ten year old manure is almost not manure any more. It almost has to be something else. I killed a garden once by adding grass clippings after having fed the grass with "Weed and Feed". Another time I used Milorgalite. (sp?) It was fertilizer from a sewage treatment plant.

[toxcrusadr]

Milorganite is from Milwaukee's treatment plant, and they have been making the stuff for decades. My dad used to talk about it way back in the 70s. They should know what they're doing and I would think their product is a fairly middle of the road compost. I'm surprised to hear that you had problems with it.

[estorms]

I got my milorganite in PA during the 70's. I put about 1/2 cup in a planting hole and mixed it with dirt. I probably used too much. It may have been improved by now. I know someone who put it on their yard, and the whole thing came up in tomatoes. I have been gardening a long time and still find new ways to kill things. My biggest problem right now is varmits.

[toxcrusadr]

www.milorganite.com says that the product is 5-_-2 with 4% iron. I could not find a K number. N and P are higher than most compost products, but it's still compost, which would be slow release. I don't see how this could harm plants in almost any amount. Is it possible something else happened to your plants?

[2cents]

I've had some 20+ yrs old cow manure that was barn stored(abandoned), it was no value. There was nothing in it and no nutrient. It added tilth, but no nutrient value.
Maybe before you got rid of it and start over, try a simple test kit to find out the NPK values, then a PH test kit.
Amend as needed

[toxcrusadr]

Correction, I meant to say there was no P number listed. Got a little dyslexic there.

I sent a request to the Milorganite site to post ALL their numbers in a prominent place on the site since they are so hard to find. I suspect they also have micronutrients and other parameters.

Re: old compost, I read a post somewhere just recently about someone testing bagged compost that had sat in their garage for 10 years. Surprisingly it still had pretty good numbers. So it all depends. I don't think this is the problem with the Milorganite though. Possibly was anaerobic if it was very wet and sat in a sealed bag for a time, and that might possibly damage plants.

[estorms]

Anything is possible. It was quite a while ago. Over the years I have killed off a lot of plants in a lot of different ways.

[toxcrusadr]

You and me both, mate!

[toxcrusadr]

I did hear back from Milorganite. Their email said the CN ratio of the product is 6:1 which is pretty high N. Great for your lawn. They still did not give me a K value so I asked them to post both CN and K on their specs page. There are also some micronutrient values there, for those interested.

https://www.milorganite.com/Using-Milorganite/Specifications.aspx