Drought-Tolerant Corn Hybrid Phenotypic Response To Plant Population and Planting Date In Ohio Environments.

Many Ohio producers have recently started planting drought-tolerant corn (Zea mays L.) hybrids to manage for in-season precipitation variability.  Persistent or protracted early-season rainfall can cause planting delays, which can increase the likelihood of moisture stress during pollination.  Drought-tolerant hybrids may be able to maintain yield per plant by improving pollination under stress conditions, and may exhibit greater tolerance for increased plant populations as compared to susceptible hybrids.  A field study was conducted in 2012 and 2013 at Hoytville, South Charleston, and Wooster, OH to compare the phenotypic response of drought-tolerant hybrids to susceptible hybrids at five populations (59,000, 74,000, 89,000, 104,000, and 124,000 plants ha^-1) and two planting dates (early May and early June), and to determine the effect of population and planting date on the anthesis-silking interval (ASI) and corn grain yields.  Four DuPont Pioneer® brand hybrids were examined: two drought-tolerant (AquaMax^TM) hybrids and two susceptible hybrids.  Phenotypic measurements of plant height, biomass, and light interception were collected at V8 to V10, R2, and R5.  ASI was determined from VT to R1, and grain yield and ear yield components were measured after R6.  In 2012, the drought-tolerant hybrid P1352 intercepted 2-8% more light at R2 than the susceptible hybrid P1184, and in 2013, 1-13% more light at V10 with no difference observed at R2.  Increasing plant population increased ASI for all hybrids in 2012, but the drought-tolerant hybrids had a shorter ASI and up to a 7% grain yield advantage under stress conditions when compared to susceptible hybrids.  Yields in 2012 were generally similar across hybrids in environments where growing conditions were more favorable, but grain yield was reduced at one late-planted site by 3%.  Plant population influenced both hybrids similarly in 2012, with maximum yields occurring at 89,000 plants ha^-1.  These results suggest drought-tolerant hybrids silk earlier than susceptible hybrids and may provide a yield advantage when moisture stress conditions are present, but perform in a similar manner to susceptible hybrids at most plant populations in favorable growing conditions.