Well, let’s face it: This is a rhetorical question. When it comes to corn, or any crop for that matter, of course we can do better. We can always improve upon what we do. But it’s also important to recognize that we have been doing better, and for some time.
Dr. Donald Duvick from Iowa State University published a review 10 years ago that looked at corn grain yield trends from 1961 to 2002 ( Duvick, 2005 ). In the United States, the average yield increase each year during that period was 1.7 bushels per acre (bu/ac).
In his review, Dr. Duvick listed several changes in genetic traits that have contributed to these steady yield increases over time. What I found interesting was that the yield potential of an individual corn plant has not changed. What has changed is that the corn plant is now able to come closer to realizing its yield potential more efficiently and under stressful conditions.
So, what stresses are modern corn hybrids more capable of withstanding? Drought, excessive moisture, root lodging, premature death, barrenness, stalk lodging, higher temperature, lower temperature, European corn borers, herbicides and higher plant density, to name a few.
As someone who studies plant nutrition, I was particularly struck by one thing in Duvick’s review: what corn plants are now doing with nitrogen. It turns out that modern corn hybrids are more tolerant of soil nitrogen deficiency. This means that where nitrogen has not been applied, modern hybrids yield better than older ones.
Does this mean less nitrogen fertilizer is needed? Data from the USDA Economic Research Service indicates that nitrogen consumption in the United States has been slowing and has been fairly static since the mid-1990s ( USDA-ERS, 2013 ); however, yields have continued to increase, meaning more yield is being produced with the same amount of nitrogen. So, basic principles of plant nutrition are still in place: Corn needs nitrogen. It’s just that we’re getting more grain for the nitrogen we apply.
How is this possible? One contributing factor may be that corn grain now has a lower protein content and more starch than it used to, as Duvick points out. Nitrogen is a building block of protein, so the less protein there is, the less nitrogen there is, too. This is also borne out in a recent study comparing grain nitrogen contents in “new era” (1991–2011) and “old era” (1940–1990) hybrids ( Ciampitti and Vyn, 2013 ). These researchers showed that grain in modern hybrids had lower nitrogen concentrations than older hybrids.
Besides genetic improvements, there have been substantial changes in the ways we manage corn. Earlier planting, higher populations, integrated pest management, site-specific management, conservation tillage and new fertilizer technologies have all been important for nudging yields steadily closer to yield potential while making better use of our resources. On top of that, the proliferation of on-farm research has helped farmers test management options under their own conditions to sift out the practices that have the best chances of working.
Can we do better? Of course. But we have been doing better for a long time, and the lesson is we don’t dare stop. Doing better isn’t just a goal, it’s a part of the farming culture. We have been and will always be reaching for those additional bushels each year.