In article ,
Tim Wescott wrote:

We have this big ol' pile of horse manure out back, which we can't
spread out in the pasture because it is full of rocks that are just
about exactly the right size for causing problems with horses feet
(according to SWMBO, at least). The sizes range from sand to 3-4 inches.

How did those get _in_ there?

Since clean, rock-free horse manure is pretty easy to get around here,
I'm assuming I cannot give it away. So I'd like to build a sifter for
the stuff, to separate the good rocks from the good fertilizer.

You could offer to deliver it, and warn about the rocks. Mind you, I do
try to go dig mine from the place that's given me the least rocks (and
weird plastic trash), but I have a truck. Even they are not rock-free,
but it's pretty occasional and usually large - they can't be bothered to
build a proper flat raised area to start the pile on, so they scoop up
crap from the (mucky) ground when rearranging it. The rocks show up in
the garden or in processing (ala rake and shovel) from truck to garden,
and get hurled in the pile with the rocks that started life in the
garden. Not such a big deal when expensive, delicate animules are not
going to step on it.

Someone else will have better details of the small rock sorting process
- big rock seem to be removed at the local gravel pit by dumping a
front-end-loader-bucketload onto a 45 degree "screen". This is quite
similar to the hand-powered screening we did at home when I was a kid,
as we dug up the garden beds and got the rocks and other detritus out
with a considerably smaller screen (of expanded metal mesh).

You idea sounds basically OK, but I suspect that it may require
considerably more engineering and investment to pull off (in a manner
that won't break in the first 5 minutes, and every 15 minutes
thereafter) than simply dumping the current pile in a horse-free-zone,
and keeping the rocks out of the next pile. Add a few pumpkin seeds to
the dumping zone and have a happy halloween...

If you have a brush pile anywhere, dump the manure pile on top of it,
and you'll save burning the brush pile if you can give it a few years.

--
Cats, coffee, chocolate...vices to live by