relationship between Soil aroma and quality?

Hello.

Last year I made a batch of compost using pine sawdust and pine needles and humanure, mostly.

That turned out the have a very sweet aroma.

This year I have a pile overwintering, made up of a nix of chopped straw, horse manure, humanure, plant materials from the previous growing season, and some of the compost that was there before.

It looks wonderful. It's dark, moist, and has a good tilth, but has no odor whatsoever.

Just curious, how important is it that it have that sweet smell, and is that sweet smell primarily the result of the specific materials used? This batch had less woody fungal elements than last year.

Would you plant into a soil that had no smell at all?

Thanks

Paul

Wow, that is an excellent question! Did you smell it under the same weather conditions as when you sniff-tested the other batch? I've noticed that flowers have way less scent in cold and dry conditions than when they are warm and moist, and I wonder it that's true of soil biota. I'd use it, but might be inclined to mix it with a little of last years batch or some dirt before top dressing with it...
Gani

gani et se wrote:Wow, that is an excellent question! Did you smell it under the same weather conditions as when you sniff-tested the other batch? I've noticed that flowers have way less scent in cold and dry conditions than when they are warm and moist, and I wonder it that's true of soil biota. I'd use it, but might be inclined to mix it with a little of last years batch or some dirt before top dressing with it...
Gani

And that is an excellent observation.

Turns out you are correct. The compost isn't as sweet as last year, but now that it's warmed up more (having brought some inside for starts) and the biology has come back to life. it has a vaguely sweet smell.

Makes perfect sense!

Thanks for responding.

Certainly straw is more bland than pine. I do not use pine , but I can tell the difference between a batch with leaves vs. straw. The leaf based mixed is far richer. Also fresh cut grass has a richer odor than using it dry.

wayne stephen wrote:Certainly straw is more bland than pine. I do not use pine , but if I can tell the difference between a batch with leaves vs. straw. The leaf based mixed is far richer. Also fresh cut grass has a richer odor than using it dry.

Ahhh... leaves are my favorite compost base.

Come to think of it, there were plenty of leaves in that first batch.

The sweet aroma in soil has been traced to glomalin, a glycoprotein produced by arbuscular mycorrhizal fungi in soil, which also acts as a sort of glue which improves tilth. I suppose that concentrations could vary, depending on compost ingredients and decomposition conditions.

wayne stephen wrote:Certainly straw is more bland than pine. I do not use pine , but I can tell the difference between a batch with leaves vs. straw. The leaf based mixed is far richer. Also fresh cut grass has a richer odor than using it dry.

Yes, straw is bland. And it tends to product a compost that is more alkaline I've noticed.

I have been impressed by the dark rich duff and soil mix under pine needles.

When I compost with the needles, it comes with loads of mycorrhiza.

You can see the white lattice in the compost.

The compost that the pine straw makes is very good for woody and some semi woody plants.

For non-woody veggies like broccoli, I use a leaf / grass based compost, which I think tends to have less fungi.