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We conducted a 9‐ha field experiment near Boone, IA, to test the hypothesis that yield, weed suppression, and profit characteristics of low‐external‐input (LEI) cropping systems can match or exceed those of conventional systems. Over a 4‐yr period, we compared a conventionally managed 2‐yr rotation system {corn (Zea mays L.)/soybean [Glycine max (L.) Merr.]} with two LEI systems: a 3‐yr corn/soybean/small grain + red clover (Trifolium pratense L.) rotation, and a 4‐yr corn/soybean/small grain + alfalfa (Medicago sativa L.)/alfalfa rotation. Synthetic N fertilizer use was 59 and 74% lower in the 3‐ and 4‐yr systems, respectively, than in the 2‐yr system; similarly, herbicide use was reduced 76 and 82% in the 3‐ and 4‐yr systems. Corn and soybean yields were as high or higher in the LEI systems as in the conventional system, and weed biomass in corn and soybean was low (≤4.2 g m⁻²) in all systems …