Is Corn Yield Increasingly Limited By Water Availability?.

Over the next decades, farmers in Ontario and the Northern Corn Belt will face increasing pressure to grow more food on less land as a result of growing population, and growing use of corn for non-food uses.  In these regions, corn yields have steadily increased since the mid-20th century.  Various management factors have contributed to this yield increase including applications of fertilizer, herbicides, earlier planting date, and higher plant densities.  Breeding factors contributing to yield increases include improved stay-green characteristics during the grain fill period, increased stress tolerance, and tolerance to high plant populations through more upright leaves and reduced lodging.  As yield has increased and non-water constraints to crop production have been removed, we hypothesized that moisture is increasingly limiting corn yield potential. Using county level yield and environmental data, we demonstrate that over the past three to five decades sensitivity of corn yield to precipitation, particularly in July and August has increased despite no changes in precipitation patterns.  These results suggest the growing importance of developing strategies for managing soil moisture in rain-fed regions.