Runoff and nutrient losses in extended and conventional crop rotations

Management systems prioritizing surface ground cover throughout the year, such as extended crop rotations with perennial phases or reduced tillage, may be more resilient to changing weather regimes associated with climate change. The purpose of this study was to determine if the benefits observed in perennial phases, including increased infiltration and reduced runoff and erosion, persisted in the annual crop phases. We conducted rainfall simulations at four landscape positions in a 7-yr rotation with ridge tillage and in a conventional corn-soybean system. From data paired by landscape position across 4 yr, the 7-yr rotation had significantly higher infiltration and lower runoff than the conventional field, although sediment and nutrient losses were similar. Runoff was correlated with ground cover, highlighting the importance of tillage practices and residue removal on the infiltration capacity of these systems. Overall, these results indicate that the lasting benefits of extended crop rotations, such as increased porosity and aggregate stability, coupled with a direct effect of increased ground cover, led to improved infiltration and less runoff during the annual crop phases.