In a 28-day dietary study, Lumbricus terrestris were placed in one quart containers with soil and offered either corn (Zea mays L.), soybean (Glycine max L. Merr.) or alfalfa (Medicago sativa) leaves, corn leaves treated with a 1:1 solution of 28% N fertilizer and deionized water, corn or soybean stalks, or no addition. The worms were weighed initially and after 28 days to determine biomass production, which was used for determining food quality. Worms exhibited large weight gains when fed alfalfa or soybean leaves, intermediate weight gains when fed corn leaves treated with N, and little or no gains for the remainder of treatments. N content of the tissues was positively correlated to biomass production. These results support the hypothesis that earthworm growth is determined by food quality, particularly N content. / Department of Natural Resources