Crop Diversity Drives Productivity and Stability in Annual Row Crops.

Annual row crops are grown across large areas of the Midwest US, often in monocultures or short rotations. Increasing the diversity of crops grown in rotations that include corn, soybean, and winter wheat may improve their productivity and resilience to climate change, and may reduce the need for economically and environmentally costly agrichemical inputs.  We tested components of this hypothesis by analyzing grain yield data from a long-term cropping system diversity field experiment that was established in 2000 at the W. K. Kellogg Biological Station in SW Michigan USA.  Treatments were increasing numbers of row and cover crops grown in rotation and ranged from one (continuous monocultures of corn, soybean, and winter wheat) to six crop species (a corn-soybean-winter wheat rotation with two cover crops annually) over a three-yr rotation. No agrichemical inputs (fertilizer or pesticides) were applied to any of the treatments for the duration of the experiment and grain yields were measured each year from 2000 to 2014. Data were analyzed to determine crop diversity treatment effects on mean annual yields and yield variability.  Corn and wheat yields were strongly affected by cropping system diversity and were highest and most stable in the most diverse cropping system treatments.  Yields of soybean were also highest in the most diverse treatments; however, crop diversity did not reduce yield variability relative to soybean monocultures.  These data suggest that cropping system diversity plays a profound role in mediating yields in annual row crops and helps to buffer these systems against year-to-year variability in weather and other environmental factors.