Ammonia smell in compost

Question

I've got a pile of hot compost going which consists primarily of:

• Straw (about 75% by volume)
• Kitchen Scraps
• Rabbit Manure
• Fall leaves and grass clippings

At the moment it's giving off a pretty decent ammonia odor when I turn it. In fact the straw (which was out in the rain and beginning to break down before it was even added to the pile), had an ammonia smell even as I was building the pile.

The broad consensus seems to be that ammonia smells indicate too much greens in the pile, i.e., a high nitrogen levels. As ready as I am to accept that this may be the case, I'm a bit confused about why the straw alone would have been smelling of ammonia since it's suppose to have something like a 75:1 ratio (C:N), which is much lower in nitrogen then the recommended 30:1 for Berkeley compost.

To complicate matters further I've just read this article which seems to contradict itself on the topic of browns and straw in particular:

Green material can be grass clippings, old flowers, green prunings, weeds, fresh garbage and fruit and vegetable wastes. Dried material can be dead, fallen leaves, dried grass, straw and somewhat woody materials from prunings.

And then...

Any material which is cut green and is allowed to dry is considered green.

Huh? Straw is definitely cut green and allowed to dry - yet it's explicitly listed as "green" and not "dried" (brown).

I was thinking of amending the pile with some very carbon heavy substance like wood chips but before I do that I'd like to understand more about why this might be happening.

UPDATE: Here's an alternate link to the pdf mentioned above since some users had trouble accessing it: http://se-59312.dev.zuma-design.com/29958.pdf

Answer 1

It's likely to do with the condition of the straw you used - straw should be completely dried out, turning from high nitrogen to primarily carbon, and that would be considered brown or carbon material. But your straw was wet and decomposing on its own with nothing else before you put in your compost because it was not stored properly; it may not have been fully dried out at that stage either, so still had a nitrogen content, in which case it was effectively a green material.

The other possibility is the amount of rabbit droppings you added in ratio to the other contents of the heap - rabbit droppings are high in nitrogen. If the smell from the heap is ammonia, then yes, you need to add carbon or browns to it and turn in well, see here https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/ammonia-odors-in-garden.htm

I was unable to access the article you provided a link to, can you add a link that works please - the extracts you provide are contradictory, so I would like to see the whole article. One other question - when you say you added fall leaves, how many were there? A large amount or just a few? Although a few leaves on a compost heap are fine, large amounts should be composted separately to make leaf mould.

Answer 2

It sounds like you're confusing hay with straw. They're different agricultural products, but non-farmers frequently are unaware of the difference, and use the terms interchangeably. (This can lead to less than satisfactory results when using the wrong one of the two, for example, if you spread hay instead of straw on your freshly seeded lawn.)

Straw is the stems of a cereal grain crop, such as wheat, oats or rice. Those crops are left standing in the field until they dry out and turn brown/tan. At the point when they're harvested, the entire stem is dead already.

photo source

Hay is just normal grass such as you would have in your lawn (usually different species of grass, but you could certainly make hay from a lawn). It's cut while green, and allowed to dry in the sun before it's collected and combined into bales or stacks. The grass plants are still alive when they're cut.

photo source

Notice the color difference in the photos. Straw is tan or golden-brown. Hay is pale green.

By the definitions you quoted above, straw is a "brown" and hay is a "green" contribution to the compost pile.