Compost lasagna fail, how do I fix it?

I was reading info on compost lasagna here, maybe I got a little too excited and acted a little too soon, lol. But I got a truck bed load of horse manure mixed with what looked like wood shavings. I put down cardboard about the diameter of a pallet & covered it with the manure & shavings mix, then cardboard, and so on for a few layers and topped it with cardboard again. I thought, "okay, that's it, now we wait a few months and I can start planting." It's been probably 5 months, I transplanted squash into it and they started turning yellow and didn't grow at all. I gave em a couple weeks and after 2 died, I moved the rest somewhere else where they're doing much better. So, I'm guessing it's not nearly broken down as it needs to be? And lacking in nitrogen still? There is still cardboard on top, it's falling apart, but I think it's been thoroughly baked by the hot sun in coastal Carolina. I was thinking about covering it in some sheet plastic and pinning it down to create heat over the mounds, would that help break it down more and maybe it'll be ready next year? Thanks so much!!

To be successful with composting no matter what method is used there needs to be a ratio of green manure with brown manure.

This manure is a vegetable manure usually.

Green grass would be green manure.  Fall leaves would be brown manure.

There are several thread regarding this on the forum so here is one:

https://permies.com/t/20074/composting/Rookie-Green-Brown-Ratio

I would start amending what you have with grass clipping, vegetable scraps for the green manure.

Since fall leaves may not be avaiable the brown manure could be straw, twigs, dead grass clipping.

I hope you will come back and let us know if you were able to salvage this into compost.

It sounds like the compost is still too 'hot' for plants to be growing in it. I have heard of some folks who, when assembling their lasagna gardens, will have a layer of intentionally placed finished compost for a few inches on top to grow in. You would be limited what you can grow with how deep the roots needed to go but at least some crops are initially obtainable.

To help speed up the composting process, I would recommend making sure the layers are staying moist. You need a level of moisture for the microbes to be happy and start munching on the organic matter. I'd be worried about just letting the pile bake dry as it will most likely slow down the process. Perhaps add a mulch layer on top to help retain moisture if you are patient? My new beds usually take about a year to settle before I'm getting decent growth in them.

Sarah, it could well be one of this issues already mentioned, but I am wondering, are you sure that the horses the manure came from weren't on a sprayed pasture or fed hay that was sprayed? Unfortunately a lot of manure can be contaminated with persistent herbicides.

Hey Jane,
I am with Timothy here. Most likely the layers weren’t wet enough. Composting needs moisture to work properly.
Manure, especially when carbon rich material is already incorporated and added (as in your cardboard) should compost well. But it needs to be moist. Otherwise it might take more than a year to mature enough to use as fertilizer, even longer to use as a planting medium.

Hey Sarah, welcome to the forums.
Horse manure, if it hasn't been aged, is going to hinder your plants' growth. Between that and what sounds like layer issues I think your plants ended up not getting a good hold in the soil. I've had similar things happen when I add a lot of sawdust/manure mix to beds, especially in hot weather these areas end up with air pockets like sponges and heat up super fast, and the roots fry (in fact I just had to fix this in some dill this week). In fact I don't use the layering method anymore for just this reason.
The good news is that next year this garden is going to be FABULOUS. you can put your heavy-feeding corn in here and it will be very happy. That nitrogen isn't going anywhere. It's just going to get better as the soil biota and mycelium eat it. In the meantime, you could tuck in extra compostables inside the layers to contribute. Throw your fall leaves on top. Hell, throw whatever you have on top.
The good thing about gardening is that most undesirable outcomes are fixable with time.

Agreed on time and moisture being essential. I've had compost fails because of letting the heap dry out. That's the most likely reason, for sure. What Sarah describes doesn't sound typical of herbicide damage, as some plants survived and could be transplanted.

But I still also think it's relevant to mention that some people composting manure brought in from off their site have experienced issues due to the manure being contaminated with persistent herbicides. I imagine horse owners may not have any way of knowing what the hay they feed the horse was sprayed with, unless they make their own hay or get it from a trusted source. Being very aware of the source of imported manure is essential.

We have never had a source of horse manure so I have only had experience with bagged well aged manure.

And I agree with the others about the moisture level.

Wouldn't adding green manure help with this?