Simple past tense and past participle of compost.(verb)
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Use "composted" in a sentence
"It's best aged or composted, which is how bagged manures are sold."
"Turn your soil and mix in some organic matter such as composted leaves and grass clippings, coffee grinds and egg shells and other composted kitchen waste."
"Lindgren said mulch can be organic (such as composted grass or leaves) or inorganic (such as plastic)."