Short corn rotations do not improve soil quality, compared with corn monocultures

Abstract

Short-duration summer annual crop rotations are widely used in the Midwest, but their long-term impact on soil quality has not been thoroughly examined. Our goal was to compare soil properties under long-term use of the most common crop rotations around Illinois, and to identify soil quality indicators for rotations in the state. Crop rotations of continuous corn (Zea mays L.) (CCC), corn–soybean [Glycine max (L.) Merr.] (CS), and corn–corn–soybean (CCS) were arranged in a randomized complete block design (RCBD), with three or four replications at each of six locations, with all phases present each year for 12 yr. We measured 21 soil properties on the surface soil and 18 properties at four successive depths, rendering a total of 126 and 504 observations available for the multivariate statistical analyses, including principal component analyses (PCA) and canonical discriminant analysis (CDA) in both data sets. We found that our discriminant rules based on the measured soil properties correctly identified the location of origin of the soil samples in 98% of cases, representing <2% error rates for the cross-validation results at each location. Crop rotations, on the other hand, did not affect any of the soil properties evaluated, results further confirmed by our CDA analyses that showed high error rates for classification. Though these short corn rotations make economic sense, they behave similarly to corn monocultures from the soil quality standpoint, compromising the sustainability of our current agricultural systems and highlighting the need to increase temporal and spatial diversification.