Crop rotation influences crop yield by changing the availability of nutrients and water, several soil properties, and incidence of pests and weeds. A crop rotation study was initiated in 1979 to assess the effects of various crop sequences and nitrogen (N) fertilization for corn on crop yield. The crop rotations are continuous corn for grain and for silage, continuous soybean, several cornsoybean sequences with one to three corn crops for every soybean crop, and corn-cornoats/alfalfa. Alfalfa is undersown with oats and only oats grain is harvested the first year. The tillage practices are chisel-plowing of cornstalks in the fall and disking of other crop residues in spring. The N treatments are 0, 80, 160, and 240 lb N/acre only for corn using granulated urea, which is spread in spring and is incorporated into the soil by disking. Grain yield was adjusted to 15 percent moisture for corn and 13 percent for soybean and oats. Biomass yield (corn for silage and alfalfa) is expressed as dry matter yield. The corn harvested for total biomass was cut 6 to 8 in. above the ground at about the black layer stage, and both weight and moisture content were determined for the whole plant.