Drought tolerant corn hybrids
In 2012 we initiated a study to determine if drought tolerant AQUAmax and conventional (non-AQUAmax hybrids) differ in their response to plant population and planting date. Various physiological traits associated with drought tolerance were also evaluated. 2012 was the warmest year on record in Ohio and the summer one of hottest and driest. However the impact of drought and heat varied considerably across the state. These conditions provided us with an opportunity to assess the response of the new drought tolerant hybrids to varying levels of stress.
The study compared four hybrids (two drought susceptible and two drought-tolerant AQUAmax hybrids) at five plant populations (24,000, 30,000, 36,000, 42,000 and 50,000 plants/A) at two planting dates (early May vs. early June). The susceptible and tolerant hybrids were characterized by drought tolerance ratings of 7 and 9, respectively, on a scale of 1-9 where 1 is poor and 9 is excellent. The study was conducted at three OSU-OARDC research stations in southwest, northwest, and northeast Ohio.
Preliminary results indicated that the grain yield of each hybrid had a similar response to plant population at each site but differed due to planting date at each location. At the NW Ohio location for the early planting date (May 3), which was subjected to the greatest drought stress, the drought tolerant hybrids out yielded the drought susceptible hybrids by 8 to 10 bu/A (about 5% averaged across plant populations). At the other locations, where drought stress was limited or absent, the drought tolerant hybrids generally yielded more or about the same as the drought susceptible hybrids.
Drought stress can delay silking and increase ASI. This “asynchronous” flowering can result in poor kernel set and inn extreme situations barren plants. In the 2012 study, measurements of flowering synchrony at the NW Ohio location for the May 3 planting date indicated that the anthesis silking interval was 1 to 3 days greater for the drought susceptible hybrids than the drought tolerant hybrids but no consistent effect of plant population on flowering synchrony was evident. On the later planting date (June 7), no difference in flowering synchrony between hybrids was present but ASI increased as plant population increased.
The preliminary results suggest that under the water stress conditions of the type experienced at the NW Ohio location in 2012, drought tolerant hybrids offered a yield advantage over drought susceptible hybrids (w/ lower drought ratings). Under more favorable conditions, the drought tolerant hybrids showed yields that were similar or slightly higher those of the drought susceptible hybrids.