Getting the Dirt on Dirt; August 1997; Scientific American Magazine; by Zacks; 1 Page(s)

It may look like just a speck of dirt to the naked eye, but under an electron microscope this crumb of prairie soil is really a carefully constructed "apartment building," home to the small critters that recycle decaying organic matter into usable nutrients. About a millimeter across, this soil crumb--or macroaggregate-- is riddled with water- and air-filled pores that shelter such organisms as bacteria, fungi and nematodes. As these organisms dine on dead roots, fertilizer and even one another, they release the nitrogen compounds that feed growing plants.

U. S. Department of Agriculture soil scientist Cynthia Cambardella is passionate about macroaggregates. She and her colleagues at the National Soil Tilth Laboratory in Ames, Iowa, study soil structure and its effect on nutrient cycling in the hope of developing more efficient and environmentally friendly farming techniques. Soils with abundant macroaggregates do a better job of supporting plant life and lose fewer nutrients to leaching; therefore, much of Cambardella¿s work focuses on the formation and degradation of these rich crumbs in agricultural lands.