Rotating corn with other crops, particularly soybeans, has long been the overwhelming choice of farmers in the U.S. and Canada. Rotation with soybeans can reduce nitrogen (N) fertilizer requirements, decrease disease and insect pressure, and allow growers to alternate herbicides.
Even when all limiting factors appear to have been adequately supplied in a continuous corn system, numerous studies have documented corn yield reductions when corn follows corn rather than soybeans. In recent years, however, the economic advantages of growing corn have prompted many growers to increase the proportion of corn acres in their operations.
A 3-year DuPont Pioneer / University of Illinois study compared continuous corn (CC), corn-soybean (CS) and corn-corn-soybean rotations (CCS) at several locations, representing a range of productivity levels.
Averaged across all sites and years, the yield penalty for CC compared to CS was 17 bu/acre, or about 9%. In contrast, the yield loss for second-year corn in the CCS rotation was only 10 bu/acre, or 5%. The 3 rotations’ yields differed only slightly across environments, despite the wide range of productivity levels characterizing the 6 experimental locations (Figure 1).
Figure 1. Corn yields obtained at 6 Illinois locations over a 2-year period using 3 corn and soybean rotations. (*, **, NS = Significant at 10% and 5% level and not significant, respectively.)
Effectively managing corn residue can contribute to successful corn-after-corn production. A corn crop produces more than twice the residue of a soybean crop. Tillage and partial stover harvest are potential management options to reduce excess residue. Effective residue management often improves stand establishment and yield.
Corn-after-corn residue allows pathogens to survive, which causes leaf diseases, stalk rots, ear rots and seedling diseases to increase. This disease pressure may be managed by selecting hybrids with high genetic disease resistance and using foliar fungicides.
Nitrogen (N) has a huge impact in corn-after-corn production. Because N is immobilized by corn residue, avoid surface N applications. Instead, band N 7 to 8 inches deep, and consider using a starter fertilizer with N.
In addition, corn-after-corn depletes the soil of phosphorus (P) more quickly and potassium (K) more slowly than corn rotated with soybean. Banding P and K or using starter fertilizers can help manage these macronutrients successfully.
Hybrid selection is an important component of successful corn-on-corn production. Growers should always be sure to select hybrids that have:
- Proven performance under diverse environments and possible stresses.
- Above average drought tolerance. (Root mass may be reduced in corn-on-corn production, which limits water uptake similar to drought conditions).
- Maturities that match corn planting date and seasonal growing degree units. (Cooler soils and slower emergence caused by high levels of corn residue should be taken into account.)