Tillage and Crop Rotation Effects on Corn Agronomic Response and Economic Return at Seven Iowa Locations

Corn yield (Zea mays L.) and economic return with different tillage systems and crop rotations are highly influenced by regional soil and climate conditions. This study was conducted at seven locations in Iowa from 2003 to 2013. The experiment design was split-plot with tillage as the main factor, which included five tillage systems (no-tillage, NT; strip-tillage, ST; chisel plow, CP; deep rip, DR; and moldboard plow, MP). Three crop rotations of corn-soybean (Glycine max L.), C-S; corn-corn-soybean, C-C-S; and corn-corn, C-C were subplots in a completely randomized block design in four replications. The objectives were to: (i) investigate seasonal variability in corn yield as affected by tillage and crop rotation, (ii) identify appropriate tillage for each crop rotation and location, and (iii) evaluate the magnitude of crop rotation effect on corn yield. Corn yields varied from 2.5 to 15.8 Mg ha(-1) with no detectable increase over time. The results showed northern locations have yield of 1.9 Mg ha(-1) and economic return of US$329 ha(-1) advantage over southern locations. Yield and economic returns for the three rotations were as follow: C-S > C-C-S > C-C. Yield and economic penalty were greater with NT than conventional tillage in the northern locations (poorly-drained soils) than locations with well-drained soils. The corn yield penalty associated with C-C was location specific and varied from 11 to 28%. The findings suggest a location specific adoption of tillage and crop rotation for achieving optimum yield.