Corn Yield-Trends from 1987 through 2015 By Yield Environments.

Average corn (Zea mays L.) yields have significantly increased in the past decades. However, there are questions on whether this overall average yield increase is result of:

(i) yield improvement across all sub-yield environments (low to high yielding) or

(ii) to a decrease in the relative proportion of low-yielding environments

(iii) to both of the above reasons or other underling reason.

The objectives of this analysis was to examine yield trends across different latitudes and yield environments from 1987-to-2015. The data for this research was originated from corn hybrid by seeding rate trials conducted from 1987-to-2015 across the US and Canada. Synthesis-analysis using hierarchical modeling was applied on this meta-data. Results from this synthesis-analysis suggest that:

(i) yield improvement was driven by yield changes at very high and high yield environments, i.e., average maximum rate of 50 kg ha−1 yr−1,

(ii) the proportion of HY and VHY corn production environments increased by 50% in the years 2007 to 2015 compared with 1987 to 1996 (the proportion of LY and MY environments has decreased over same time).

(iii) yield for medium-yielding (MY) and LY environments did not significantly change over time,

In summary, increases in the yield ceiling and proportion of HY environments were the main reasons responsible for yield improvement. Future research might continue to focus on yield improvement and further shrinking of LY and MY environments via improved hybrid and crop management technologies.