Spent grains and hops

[jonos7]

So I put all my spent grains from brewing on top of my hop mounds thinking that it would be a great mulch and it would keep water in. Now the grains started to mold, will this mold be a problem?

 

[damdaman]

You'd want to compost your spent grains and hops before putting them on your plants. Decomposing organic matter like that create large flushes of microorganisms that will often leech nitrogen from the soil.

Not to mention it attracts pests like rats.

 

[B-Hoppy]

I don't really think the mold will cause any harm and if you spread them a little thinner and break it up to get some air mixed in the mold will probably go away on it's own. I personally compost the grains first but they do contain a good bit of nitrogen so I don't know if it really matters. I wouldn't sweat it though.

 

[oakbarn]

I compost my spent grains among other uses. They do stink after a while but compost nicely. Do not use to put on your hops until fully composted (Looks like black dirt). You could kill them if you put on before composting.

 

[Hop_Hero]

I too compost my grains however about once a week I'll mix some used coffee grains into my garden soil. Not too much. I was told it would boost nitrogen and also repel snails and a few other pests.

 

[bigljd]

I compost my spent grains among other uses. They do stink after a while but compost nicely. Do not use to put on your hops until fully composted (Looks like black dirt). You could kill them if you put on before composting.

Not sure how using spent grains to mulch plants could kill them. If he mixed uncomposted spent grains into the soil, the microbes that would decompose the grains would leach nitrogen from the soil and could affect the plant health, but spreading organic material on the surface as a mulch shouldn't hurt anything as long as it's not too thick

It probably will attract rats/racoons/opossums though, and I would be concerned with them damaging the plants. It is best to compost first.

 

[odinsgift]

Spent grains are best used directly mulched, as opposed to composted, if a nitrogen amendment is what you're looking for.

 

[wrench]

Spent grains are best used directly mulched, as opposed to composted, if a nitrogen amendment is what you're looking for.

Can you back this up? It seems to contradict what I know about organic nutrients. From what I understand, microorganisms need to "chew up" the spent grain (or any other similar material) in order to free up the Nitrogen for use by the hops. That's why compost is a slow-release fertilizer. Chemical fertilizers are quick because the Nitrogen is already in a form that plants can use. If I'm right, the bulk of the Nitrogen is only available to the plant AFTER composting.

 

[odinsgift]

I believe you lose some usable nitrogen if it does not stay in the same place. It will decompose just the same in the soil as in a compost pile, in my opinion.

 

[garnede]

Grains are a nitrogen rich supplement, but they might need to be mixed with some carbon rich organic mater to prevent problem molds. That said Mold, fungus, and bacteria are what breaks the organic mater down into a useable nutrients by your hops. Just don't let the molding grain touch your bines, which might cause a fungal disease.

You'd want to compost your spent grains and hops before putting them on your plants. Decomposing organic matter like that create large flushes of microorganisms that will often leech nitrogen from the soil.

Not to mention it attracts pests like rats.

By composting your grains first you will loose some nitrogen to the bacteria that eat and break down the grains. A hot compost will make you loose more than a long cold compost. Hot compost is better for soil texture and cold compost provides more nutrients. By the same token those micro organisms will die and return the nitrogen they consume to the soil. Leaching is caused by water flow. Those bacteria actually prevent leaching by holding the excess nutrients in their bodies, some have symbiotic relationship with the plants and exchange nutrients for sugars from the plants. The others release the nutrients when they die. You want a healthy bacteria and fungal population for the health of your plants.

 

[damdaman]

By composting your grains first you will loose some nitrogen to the bacteria that eat and break down the grains. ... The others release the nutrients when they die.

Exactly why you should compost first. The nitrogen comes from the dead microorganisms. The micros consume nitrogen to feed their bodies, and then when they die, they enrich the soil. The nitrogen in your spent grains is not available to the plants until the micros free it and then die.

The problem is that the micros usually require more nitrogen than the soil amendment, in this case spent grains, supplies. They then use nitrogen from the soil to "top up." This creates a temporary nitrogen shortage in the top soil, followed by a nitrogen flush once the matter breaks down.

If you compost first, you get just the flush, without the original shortage. And you avoid pests.

 

[jonos7]

Thanks, for now I think I'll just scrape the grains away from the plants and call it good, might add a little dirt over the top of whats left.

 

[SteveBeitz]

Please note that if you have a dog - do not compost hops - hops are toxic to dogs and can kill them! It's not worth the risk of your dog getting into them.

 

[oakbarn]

Not sure how using spent grains to mulch plants could kill them. If he mixed uncomposted spent grains into the soil, the microbes that would decompose the grains would leach nitrogen from the soil and could affect the plant health, but spreading organic material on the surface as a mulch shouldn't hurt anything as long as it's not too thick

It probably will attract rats/racoons/opossums though, and I would be concerned with them damaging the plants. It is best to compost first.

Too much un composted material will not support plants. If you add too much compost, you can kill you plants. How? I do not know but that is experience talking as I had some plants doing nicely and then ....

Could have been something else, but I no longer do it.