Visual Soil Structure Effects of Tillage and Corn Stover Harvest in Iowa

High levels of corn (Zea mays L.) stover harvest for ethanol production have raised concerns regarding negative consequences on soil structure and physical quality. Visual soil structure assessment methods have the potential to help address these concerns through simple, straightforward on-farm evaluations. Our objective was to determine if the visual evaluation of soil structure (VESS) approach could detect soil structural quality differences associated with different levels of corn stover harvest and tillage practices. We evaluated no harvest and moderate and high stover harvest levels within no-tillage (NT) and chisel plow (CP) plots following 7 yr of continuous corn. Undisturbed 10- by 20- by 25-cm soil samples were taken using a spade in April 2015. The thickness and structural quality (Sq) scores for the 0- to 5- (top) and 5- to 20-cm (bottom) soil layers were determined, and an overall Sq was computed. The Sq values showed a significant interaction between corn stover harvest and tillage practice. Soil structural quality showed no significant differences between NT and CP systems for either the no-or moderate-harvest treatments, but with a high stover harvest rate, CP structural quality was worse than NT. With NT, both moderate and high rates of stover harvest significantly increased Sq compared to no harvest; in CP, there was no significant difference between the no-and moderate-harvest treatments. Only a high level of stover harvest had an adverse effect on the Sq rating. The VESS approach was sensitive for detecting the effects of corn stover harvest and tillage systems on soil structural quality and should be further evaluated as an integrative, on-farm soil quality/health indicator.