Tillage and crop rotation impact on soybean grain yield and composition

Soybean [Glycine max (L.) Merr.] yield response to tillage and crop rotation has varied among studies. Information regarding the effects of crop rotation and tillage on protein and oil concentrations in soybean grain is limited. A 3-yr field study was conducted near Arlington, WI using conventional tillage and no-tillage systems in seven soybean and corn (Zea mays L.) rotations. The objective was to determine the effect of tillage system and crop rotation on the yield, protein concentration, and oil concentration of soybean grain. The tillage X rotation interaction was significant (P <= 0.05) for grain yield. In the no-tillage system, yields dropped 42% from 4.00 Mg ha(-1) in first-year soybean following 5 yr of consecutive corn to 2.33 Mg ha(-1) in continuous soybean. In the conventional tillage system, yields dropped 35% from 3.01 Mg ha(-1) in first-year soybean following 5 yr of consecutive corn to 2.04 Mg ha(-1) in continuous soybean. The tillage X rotation interaction was significant (P <= 0.05) for protein concentration. In the conventional tillage system, protein concentration decreased from 357 mg kg(-1) in first-year soybean following five consecutive years of corn to 351 mg kg(-1) in fifth-year soybean following five consecutive years of corn. No clear trend was observed for protein concentration in the no-tillage system. Oil concentration increased as consecutive years of soybean production increased in both tillage systems at a similar rate.