Comparison of Yield Components and Physiological Parameters of Drought Tolerant and Conventional Corn Hybrids

CORE IDEAS: Drought‐tolerant corn hybrids did not out‐yield conventional corn hybrids. No yield components differed among hybrids. Corn (Zea mays L.) consumes large quantities of water to produce yield. When sufficient hectares within an area are irrigated using deep wells, corn production can contribute to depleting underground aquafers. Hybrids genetically engineered for drought tolerance have recently become available to producers. Six hybrids, three sold as drought tolerant, were evaluated for yield, yield components, and physiological parameters of net assimilation rate (A), stomatal conductance (gₛ), transpiration rate (Em), intercellular CO₂ (Ci), and intrinsic water use efficiency (IWUE) during early reproductive growth in 2014 through 2016 with irrigated and nonirrigated treatments applied after anthesis. Irrigation did not improve yields among hybrids in any year. Hybrid differences in yield occurred each year but with no consistency across years, and genetically drought‐tolerant hybrids were not always superior. Mean yields by year were 2016 (12,590 kg ha⁻¹) > 2015 (10,214 kg ha⁻¹) > 2014 (7843 kg ha⁻¹). Low yields in 2014 are attributed to fewer kernels per plant due to possible Formesafen herbicide carryover applied to soybean (Glycine max L. Merr.) the previous year. Of the physiological parameters measured (A, gₛ, Em, Ci, and IWUE), no hybrid differences were observed, only Em was found to be greater at anthesis (R1) than at kernel filling (R2), and irrigated treatments had greater Em than nonirrigated treatments. Data from this experiment and its environmental conditions showed no yield or physiological differences between drought‐tolerant and conventional corn hybrids. Only on nonirrigated fields during limited soil moisture would drought‐tolerant hybrids possibly be beneficial. Any reduction in irrigation by growing drought‐resistant hybrids could not be determined in this experiment.