Soil Attributes, Soybean Mineral Nutrition, and Yield in Diverse Crop Rotations under No-Till Conditions

Development of sustainable crop rotations depends on understanding complex relationships among soils, crops, and yield. Our objectives were to measure how soil chemical and physical attributes as well as soybean [Glycine max (L.) Merr.] stover dry weight and mineral concentrations, seed yield, and seed composition (protein, oil, and minerals) responded to a soybean-maize (Zea mays L.) 2-yr rotation (S-C), soybean-spring wheat (Triticum aestivum L.)maize 3-yr rotation (S-W-C), soybean-oat/pea (Hordeum vulgare L./Pisum sativum L.) hay-maize 3-yr rotation (S-H-C), and soybean-oat/pea hay underseeded with alfalfa (Medicago sativa L.)-alfalfa-alfalfa-maize 5-yr rotation (S-H/A-A-A-C). Rotation treatments under no-till soil management were established in 1997 and soybean measurements were made during the 2009 and 2010 growing seasons. Soils under the 5-yr rotation had 129 kg ha(-1) preseason residual NO3-N concentration, while the other rotations averaged about 65 kg ha(-1). The 5-yr rotation also had lower bulk density (1.35 g cm(-3)) than S-H-C (1.46 g cm(-3)), with S-W-C (1.38 g cm(-3)) and S-C (1.38 g cm(-3)) intermediate. Soybean seed yield was about 10% greater in the 5-yr rotation than in the other treatments. Kernel protein was 3% greater and kernel Zn was 11% greater under the 5-yr rotation than under the S-C rotation, while the others were intermediate. Changes in soil physical and chemical properties under extended rotations that include perennial forages may play an important role in increasing soybean seed yield and enhancing seed protein but may, because of high preseason soil NO3-N levels, also be susceptible to potential NO3-N leaching beyond the root zone.