The final predictor of the CCYP, difference in CC and CS delta yields (the difference between the yield where no N was applied and the maximum yield under non-N limiting conditions), is probably a function of weather conditions, particularly during critical growth periods such as ovule determination and grain fill. Drought and heat can disproportionately reduce yields of the CC system relative to the CS system. This principle was demonstrated during the 2012 drought, when farmers reported yield reductions as large as 50 bushels per acre for CC systems compared to CS.
Based on this study, the authors concluded that the CCYP persists for at least seven years. However, during very favorable growing seasons, increased N rates can overcome the CCYP. Unfortunately, higher N rates do not eliminate the CCYP during average or poor growing seasons. This study concluded that the primary causes of the CCYP are: N availability, corn stover accumulation, and unfavorable weather.
“Given that weather cannot be controlled, and the optimum N fertilizer rate can be determined only after crop harvest, managing corn stover has the greatest potential for reducing the CCYP,” said Gentry. The same research team is collaborating on a follow-up study investigating the effect of stover removal and tillage on the CCYP.
“Identifying Factors Controlling the Continuous Corn Yield Penalty” was published in the January 2013 issue of Agronomy Journal (105:295-303). It is an open-access article available at: https://www.crops.org/publications/aj/articles/105/2/295