Do you have s spot where you could stockpile and use as needed?

I could just keep it at my brother's house... keep in mind that the receipt of this "gift" requires a bit of quality time between me, my truck, a shovel, and a man-height pile of compost! My back might prefer that more remain in the pile than on my gardens. But... the opportunity is there if it turns out that adding 12" of compost to all my beds is a good idea.

I think 12" might b too much but you might get away with 1/2 of that. I take it there is no room in your prop. When it can sit for a while.

Kinda depends on what you are starting with. If the soil has very little organic matter, it might be OK if tilled in deep enough, but if you have already been amending over time and have good soil to start with...I'd spread it on my lawn if I had that much. Does wonders for lawns.

A level of organic matter in soil of about 6 to 8 percent is optimal. To get to that level requires a lot of organic material, compost is one source.

How much, if any, organic matter is in that soil now?

Too much organic matter in soil can be detrimental rather than helpful because the soil then could retain too much moisture which will cause more problems.

Perhaps these simple soil tests may be of some help.

1) Soil test for organic
material. From that soil sample put enough of the rest to make a 4 inch level in
a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and
replace the lid, tightly. Shake the jar vigorously and then let it stand for 24
hours. Your soil will settle out according to soil particle size and weight.
For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the
bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above
that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole
1 foot square and 1 foot deep and fill that with water. After that water drains
away refill the hole with more water and time how long it takes that to drain
away. Anything less than 2 hours and your soil drains’ too quickly and needs
more organic matter to slow that drainage down. Anything over 6 hours and the
soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful
of your slightly damp soil and squeeze it tightly. When the pressure is
released the soil should hold together in that clump, but when poked with a
finger that clump should fall apart.

4) Smell. What does your
soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant
odor? The more organic matter in your soil the more active the soil bacteria
will be and the nicer your soil will smell, to a point. Too much organic matter
can be bad as well.

5) Life. How many
earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5,
according to the Natural Resources Conservation Service, indicates a soil that
is not healthy.

kimmq is kimmsr

Why not spread the rest on your grass?

I think the 6 to 8 percent figure was arrived at assuming it is all compost. Then 6-8% hits a good balance of nutrients. Prairies can have 20%, but it is more carbon, with the micros cycling continuously. At any rate, for me, at 20% compost, my nutrient levels are too high for optimal chemical balance.

glib, that 6 to 8 percent level is organic matter, the residual of organic material put into soil. A level of organic material of 20 percent would be reduced by the Soil Food Web to a much lower level over time.

There is a difference between organic material, what you add to soil, and organic matter, what is left of that organic material after the SFW w9orks on it.

kimmq is kimmsr

No, no, my soil test says 20% OM. And chernozem also can get there. If you reapply compost every year then, it will stay at 20% (with possible induced chlorosis in some cases). Maybe they should just measure carbon, and respiration rates.

seed starting medium can often be 100% compost, (that has been sterilized to eliminate pathogens for seed germination). if its completely broken down and reached high temperatures, I'd say go up to 50%, but spread it out so it doesn't get anyone place too hot. its real benefit is being mixed into your soil (cation exchange capacity) not as a top dressing. if you don't use it all, cover it with seed from a winter kill cover crop like oats, so you don't lose all your nitrogen (transpiration/unbonding) or have it erode.

I'm not sure you can have too much compost.

Too much compost, or organic matter, in soil is not a good thing anymore than too much fertilizer is. Ma Nature makes soil that is often balanced, as anyone that has ever sampled the soil in a forest will know.

Excess amounts of compost in soil can cause pollution just as too much fertilizer will.

kimmq is kimmsr

So maybe I should take some off your hands.