Drought events are predicted to increase with rising global temperatures and altered rainfall patterns. It is important that agronomists investigate ways to maximize water use to help reduce grain yield losses from drought events. If Ohio corn yields had been reduced 10% in 2013 due to drought, then the economic loss for growers would have exceeded $250 million. Ohio producers have begun using drought-tolerant corn hybrids that were developed for use in the Western Corn Belt to manage for drought events, but limited research has been conducted on these hybrids in the Eastern Corn Belt. Drought tolerance can be thought of as the ability of a plant to produce greater yields under water stress conditions when compared to other plants under the same conditions. Since growing conditions are very different in Ohio than in the Western Corn Belt, the management practices that maximize grain yield and minimize environmental effects need to be determined for these corn hybrids. Drought-tolerant hybrids may respond to planting delays and higher plant populations (the number of plants per unit area) differently than susceptible hybrids. Under non-water stressed conditions, these corn hybrids may produce less grain yield that their susceptible counterparts (resulting in a yield penalty). Because water use efficiency and nitrogen use efficiency are related, these drought-tolerant hybrids may require a different amount of nitrogen (N) to maximize yield, which could influence environmental losses of N.
There has been little research on the modern drought-tolerant corn hybrid physiology, and measuring physiological characteristics such as net photosynthesis, stomatal conductance and chlorophyll fluorescence ratios may help identify the drought-tolerance mechanism(s) in these hybrids. Two field experiments were developed to investigate these problems. The first examined N use efficiency and minimum N required to maximize grain yield for four hybrids (two drought-tolerant hybrids and two non-tolerant hybrids) at two Ohio locations over two years. The second investigated how the same hybrids responded physiologically to increasing plant density, or plants per unit area (five different levels), and planting date (early versus late) at three Ohio locations over three years. The research was supported in part by an OSU-Ohio Agricultural Research and Development Center SEEDS Grant and a Pioneer Crop Management Research Award and the experiments were conducted at OSU research farms near S. Charleston, Hoytville, and Apple Creek, Ohio.
The drought-tolerant hybrids had similar ear-leaf N uptake and yield response to N application as compared to the susceptible hybrids. At most planting dates and locations, there was no yield difference between the drought-tolerant and susceptible hybrids. In three of the 12 environments (for 2012-2103), a 5-10% yield advantage occurred with the drought-tolerant hybrids. In one of the environments a 2% grain yield penalty was observed in the drought-tolerant hybrids compared to the susceptible hybrids. At some of the locations, the photosynthetic rates in the drought-tolerant hybrid were similar to the susceptible hybrid, but the same plants had reduced stomatal conductance indicating water use efficiency may have been increased. In the vegetative stages, chlorophyll fluorescence ratios tended to be greater in the drought-tolerant hybrids, which could indicate less plant stress in the vegetative stages. All hybrids exhibited a similar grain yield response to population density, and planting date, which indicates the drought-tolerant corn hybrids can be managed in Ohio environments using current production recommendations.
These results help to identify improved water use efficiency and less plant stress during vegetative growth as two possible mechanisms for greater drought tolerance. Additionally, they provide Ohio producers with recommendations based on research conducted in multiple locations and years on how to utilize these tools to manage for climate change and remain competitive in a global economy. Future research should investigate if the physiological characteristics observed are similar in other corn hybrids. Additionally, the effect on grain quality is currently under investigation to see if the differences observed physiologically altered protein, oil, and starch content in the grain.