The Impact of Crop Diversity on Soil Health and Crop Production.

Traditionally in the northern Corn Belt crop rotations consist of corn/soybean with little if any small grains included.  This short two-year rotation has resulted in significant problems with various pests (weeds, insects and disease).  A field experiment located near Brookings, SD was established in the fall of 2000 to evaluate the impact of diversified four-year crop rotations on crop production and soil health.  The experimental design was a randomized complete block with four replications.  Multiple 4-year rotations were evaluated with crops including corn, soybean, winter wheat, spring wheat, oat, dry pea, canola, and sunflower.  Plots were set-up such that each phase of the rotation was present each year.  A corn/soybean rotation was also included for comparison purposes.  Soil aggregate distribution and soil organic carbon were utilized as indicators of changes in soil health. Results found that there was a significantly larger erodible fraction for 2-yr corn/soybean rotation compared to the 4-yr rotation including winter wheat or sunflowers.  Crop rotation with sunflower and the 2-yr rotation had a greater increase in soil organic carbon over the life of the experiment. Throughout the experiment there were no significant difference in corn yield between the different rotation lengths, but soybeans had a significant increase in yield when grown in the 4-yr rotations compared to the 2-yr corn soybean rotation.