Drought Tolerant Corn Hybrid Response to Nitrogen Application Rate.

Multiple seed companies have released a new generation of drought-tolerant corn (Zea mays L.) hybrids, which are marketed as capable of maintaining grain yield under water stress conditions better than other hybrids. However, water use efficiency and nitrogen (N) use efficiency (NUE) have been shown to be inversely related and changes in the water relations of drought-tolerant hybrids could affect their N response. A field study was conducted in 2013 and 2014 in Northwest (NWARS) and Western (WARS) Ohio to measure the responses of two drought-tolerant hybrids and two non-tolerant hybrids to sidedress N application rate (0, 67, 134, 202, and 269 kg N ha^-1). Relative chlorophyll content (SPAD) and ear-leaf N content was measured at R2 for each hybrid. Grain yield and protein, oil, and starch content were measured at R6. The relative chlorophyll content of each hybrid exhibited a similar response to N rate with maximum content occurring at 134 kg N ha^-1 at both sites in 2013. One drought-tolerant hybrid had lower relative chlorophyll content at WARS in 2013. Ear-leaf N content was greatest in one non-tolerant hybrid compared to all others at each site. Maximum ear-leaf N concentration occurred for all hybrids at 202 and 134 kg N ha^-1 at NWARS and WARS, respectively, and corresponded with maximum grain yield. Protein content in the grain increased by 18 g kg^-1, starch content decreased by 15 g kg^-1, and oil decreased by 5 g kg^-1 as N rate increased. The drought-tolerant hybrids consistently had greater oil and lower starch grain content as compared to the non-tolerant hybrids. Hybrid differences in grain quality were evident, but the changes in quality due to N were consistent. This research suggests that drought-tolerant corn hybrids exhibit similar N responses to non-tolerant hybrids, and can be managed using existing N recommendations.