Screening Your Compost

[AyatollahGondola]

I have been screening our finished compost using various methods. What I'm wondering is whether letting the compost dry out for easier screening might be harming the value of the end product. Obviously it clumps up when it's wet or damp, but I'd rather suffer that than harm the product.

My last screening methods are using a coarse mesh shaker first, and then a finer screen for end. It goes faster if it is allowed to dry.

[tomc]

For compost a bottomless box built out of 5/4 lumber and 1/2" hardware cloth bottom, fits on top of my wheelbarrow. Where I can drag a shovel (over) or shake the whole box riding on the barrow.

It aint worth using a finer screen, and may not percolate as well as a bigger grain compost will.

[JC's Garden]

I have a coarse section, 1/2" hardware cloth, for every day use and the fine section, double layered 1/2", for seed starting.

I've read that working with wet organic matter tends to damage the humus. True? I don't know, but if I'm going to work that long on compost, I'll let it dry first.

[rainbowgardener]

Why do you need your compost so fine? Are you making potting soil with it? Other than that, there is no reason to have it so fine. I rough sift mine, mainly to get sticks and stuff out.

And yes, I think dried compost will be much less biologically active than fresh. Will all those organisms revive when the compost is rehydrated? I don't really know, but my guess would be some but not all.

[toxcrusadr]

Humus works on a microscopic scale in the soil, gluing soil particles together and so forth, so I don't see how sifting it can damage it any way.

I normally don't sift at all when it's being dug into the garden or used for top dressing. Just throw big uncomposted chunks back into the pile. If I'm making a very fine seed bed in the spring, I might screen it through chicken wire (fairly coarse). Finer than that, only for potting soil.

[rainbowgardener]

I wasn't suggesting the sifting changes anything, just a lot work.

There was a question back there about letting it dry out. I do think drying it out changes things, just as it does in the pile. It's why I water the compost pile when I water the garden, to keep it from drying out.

[AyatollahGondola]

I screen it to get the best compost out, and return the undigested stuff back to the compost pile. But....yes I do like to have some for finer planting jobs.

[tomc]

I am taking the position that sifting changes the mechanics of soil, making it more compact-able and more likely to become anoxic (have no air). Which in pots makes it less viable (less livable for plants).

Sift a little for a top layer and knock off with the sifting, its not bringing you home.

[applestar]

I pick out big sticks, etc. then use the chunky compost with incompletely digested ingredients still in it for building new beds,
A wire fence -- I think 1-1/2 x 2-?" to get larger chunks out when using the compost to plant with,
Another wire fence -- 1"x 2" for using in container mixes (I just pick out pieces too big for smaller containers and save them to use in bottom portion of bigger containers)
1/2" square riddle for seed starting mix.

...1/2" square will catch the bigger earthworms which I don't want to squish into soilblocks...

I agree with rainbowgardener that drying would likely slow down or terminate the microbial activity. Living compost needs to stay at least somewhat moist, and the container should have breathing holes.

Larger particles and chunks contain volumes of micro pores where the microbes can live, and air supply, too. But I agree with tomc that different aggregate sizes create the necessary well-draining, non-compressing medium.