Best types of maize hybrids for the western High Plains of the USA
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Maize (Zea mays L.) production in the western High Plains of the USA occurs under dryland and irrigated conditions. Thus, an ideal maize hybrid for this region would have stable and high average performance across environments that are highly variable in productivity. Stability of a hybrid in this research was defined as its across-environmental variance. Nine commercial single-cross hybrids and 36 related double crosses were evaluated for grain yield in four irrigated and eight dryland environments in Nebraska, Colorado, and Wyoming. Environmental means ranged from 2.10 to 12.01 Mg ha-1. The average superiority of the single crosses over the double crosses in mean grain yield was 11.5%. However, the double crosses were generally more stable than the single crosses. This was true regardless whether stability was measured across all 12 environments or only across the eight dryland environments. The greater stability of the double-cross hybrids in the dryland environments was the result of fewer extremely low or high yields compared with the single crosses. Hybrids were ranked considering both stability and mean performance with a safety-first index. Values of this index depended on the value chosen for acceptable minimal yield. Across all 12 environments, a double-cross hybrid ranked the best when the minimal acceptable yield was <2.68 Mg ha-1, and across the eight dryland environments this happened when the minimal acceptable yield was <1.88 Mg ha-1. Possible use of other types of heterogeneous maize hybrids in the Western High Plains are discussed.
