Where Did My Compost Go? Understanding Soil Organic Matter Loss

Three years after amending heavy clay with half a ton of compost, you dig to find mostly clay again. Where did the organic matter go? Several processes are at work: surface particles blew away as dust, rain washed away lighter compost, and soil organisms consumed larger fragments, excreting tiny humus particles that pack down with clay.

Think of compost like vegetables in a slow cooker—after three years, you're left with thin gruel, not recognizable pieces. The humus remains beneficial, holding nutrients for plants, but it doesn't maintain the loose, friable texture gardeners love.

Reverse the decline by applying a one-inch layer of composted cow manure around perennials and shrubs, keeping it away from stems, and covering with pine straw. Earthworms will gradually incorporate it. Your original tilling oxygenated the soil and attracted organisms; now you just need to keep feeding them. Check next spring—if the manure is gone, it's time to feed the soil again.