The compact, thicker root system from the Eastern, Northern, Early Health and Late Health Genetic Families (on the left) is able to penetrate hardpan areas. The fibrous root mass on the right comes from a hybrid that was incorrectly placed in a heavy clay soil environment.
Hybrids are selected for strong drought tolerance, even when planted at a high plant population. This is important in the western Corn Belt where low plant population is used as a hedge against drought. Low population strategy means using only flex-ear hybrids providing good yields at low plant populations, such as Southern, Western, Tropical and High Yield genetic types.
Plant breeders have successfully selected for drought-tolerant genetic sources. These genetics allow growers to plant higher-yielding, fixed-ear hybrids that require aggressive plant populations, even in the western parts of Iowa, Minnesota, the Dakotas and Nebraska. These hybrids prioritize moisture movement to the silks at pollination, which allows silking that is synchronized with pollen shed. They are more likely to form ears during hot, dry weather because they start with a well-pollinated ear. Eastern, Northern and Western genetic types have strong silking genetics. In the western drought-prone areas of South Dakota and Nebraska, the Western genetic type silks strongly and performs especially well.
Southern genetic types are the slowest silking during dry weather. Therefore, they should be planted at lower populations in drought-prone areas to conserve moisture for the pollination period and reduce their drought risk. Due to longer ears and higher moisture requirements for additional silk development, Southern types are the first to show unpollinated tips when stressed during the flowering stage. Roundup Ready® no-till systems using large, flex-ear Southern genetic hybrids can be a good way to reduce risk and still generate high yields in the drought-prone western Corn Belt.
Tropical types, because of the areas where they were developed, have strong tolerance to heat. But tropical areas have plenty of moisture, and strong heat tolerance does not necessarily mean strong drought tolerance.
To achieve strong drought tolerance without reducing population, select hybrids that tassel and silk in synchrony, even under dry conditions. Conversely, some large-ear hybrids may require a reduced population to lower their drought risk. It depends on genetic family.
- The High Yield Genetic Family produces a highly fibrous, spreading root system, adding drought tolerance and root lodging resistance. However, this type of root system does not penetrate heavy, sticky, clay-loam soils.
- Eastern, Northern, Early Health and Late Health Genetic Families have more compact root systems with fewer but thicker roots tending to go straight down and penetrate hardpan areas. Their smaller root systems give up drought tolerance and root lodging resistance, but in heavy, tight, wet clay soils, they can grow in areas where spreading, fibrous High Yield Genetic Family root systems cannot grow.
- Farther west in the Corn Belt, the spreading, fibrous root system of the High Yield Genetic Family can add more value by delivering drought tolerance, and its disease limitations carry less risk because the environment is not as favorable for disease development.
- The Early Health and Late Health Genetic Families can add value by delivering disease resistance and smaller root systems farther east in the Corn Belt, where rain is more plentiful.