Fig. 1. Performance scores (scaled to 100) from 1983–1990, 1983–1994, and 1983–1998 for four crop sequences organized by N rate. ZERO, LOW, and HIGH N rates represent 0, 90, and 180 kg N ha^-1 for corn and grain sorghum and 0, 34, and 68 kg N ha^-1 for soybean and oat + clover. CC, continuous corn; C–SB, corn–soybean; C–OCL–SG–SB, corn–oat + clover–sorghum–soybean; C–SB–SG–OCL, corn–soybean–sorghum–oat + clover.