When soil particles stick together, they form clumps--or “soil aggregates” as they’re called in the science biz. In a healthy soil, clumps cannot be easily broken apart by falling rain or the blade of a plow.
Soil clumps form when microscopic creatures in the soil gobble up organic matter (dead animal and plant matter). As microbes eat organic matter, a substance is formed that helps soil particles stick together.
A student plays with a clump of silty soil. (“Silt” is a type of soil particle.) A healthy soil has soil clumps that are not easily busted apart by rain and wind.