A 22-acre field experiment was conducted in Boone, IA, from 2003–2006 to test the hypothesis that low-external-input(LEI) cropping systems can produce yields and profits that match or exceed those obtained from conventional systems. A conventionally managed 2-year rotation system [corn (Zea mays L.)/soybean (Glycine max (L.) Merr.)] was compared with a 3-year LEI rotation system [corn/soybean/small grain + red clover (Trifolium pratense L.)], and a 4-year LEI rotation system [corn/soybean/small grain + alfalfa (Medicago sativa L.)/alfalfa]. Triticale (× Triticosecale Wittmack) was used as the small grain in 2003–2005; oat (Avena sativa L.) was used in 2006. Over the period of 2003– 2006, synthetic N fertilizer use was 59% and 74% lower in the 3- and 4-year systems, respectively, compared with the 2-year system. Similarly, herbicide use was reduced 76% and 82% in the 3- and 4-year systems
