Enriching a soil's nutrition and CEC (cation exchange capacity) by adding decomposed organic matter to it. Grass clippings, kitchen scraps, coffee grounds, and even certain kinds of weeds will serve when mixed with brown matter (dry twigs, newspaper), but not animal fat, meat, oil, or cat or dog feces. A properly built, moistened, and aerated pile will gradually heat up as microorganisms break it down into humus; for faster results, shred the materials before composting, keep sponge-moist, and turn the pile every three days, shoveling undigested matter at its edges into its baking heart. It is ready to spread on soil when flaky brown and no longer hot. A thin layer of soil on the pile gets it off to a start. A pile of less than three cubic feet may not heat up properly.