Is Rotated Corn Better than Continuous?
|Fred E. Below
Professor of Crop Physiology
Department of Crop Sciences
|Allen W. Becker
Graduate Research Assistant
Department of Crop Sciences
The standard for the past 50 years in Illinois has been to grow corn in rotation with soybean. Rotating crops provides a number of benefits such as pest control, market flexibility, and generally higher yields. While the yield advantage of rotated corn has been well documented, some recent high-yield contests have shown that it is possible to achieve record yields with continuous corn. The objective of this study was to identify plant factors associated with better performance of rotated corn (or poorer growth of continuous corn) that could be altered by management practices. We grew 22 commercial hybrids with either corn (3rd year) or soybean as the previous crop, and varied the level of fertilizer N (six rates between 0 and 240 lbs/acre), and the timing of tillage (fall and spring). There was a large impact of previous crop on seedling emergence of all hybrids, with rotated corn averaging 85% emergence compared to 73% for continuous corn. Previous crop also affected early vegetative growth, and by V8 rotated plants were 21% larger than those following corn. This difference persisted throughout vegetative growth and shows how quickly yield can be penalized in continuous corn early in the season. The poorer vegetative growth of continuous corn could not be overcome with additional N, but if the previous crop was corn, tillage in the fall improved plant growth (by 17%) compared to tillage in the spring. In contrast, if soybean was the previous crop, tillage timing (i.e. fall vs. spring) had no impact on any of the measured parameters. Grain yield was also lower for continuous corn (average of 25 bu/acre), especially for corn residue tilled in the spring (6 bu/acre lower for spring compared to fall tillage). While the N supply clearly impacted grain yield in both previous crop scenarios (increasing about 25 bu going from deficient to sufficient), additional N could not overcome the yield penalty associated with continuous corn.
View of our experimental site with continuous corn in the foreground and rotated corn in the background (note the taller plants). Plants are at the V8 growth stage.
Despite considerable variation among the 22 hybrids for all parameters, there were no individual hybrids that performed relatively better than the others under continuous corn. Our findings show that rotated corn is better than continuous largely due to detrimental effects of the corn residue. We suggest that residue management should be a major goal in continuous corn production, along with selecting a high-yielding hybrid, planting it at an adequate stand, and applying the proper amount of N.