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Soil fertility levels will influence the choice of genetic family.
If the goal is winning a yield trial, a large-ear High Yield x Southern hybrid placed on a well-drained, high-fertility field with an aggressive nitrogen program is the right choice. Nitrogen-driven Southern genetics continue to absorb nitrogen later in the growing season, after flowering and later into grain fill, than hybrids made with other genetic families. This late-absorbed nitrogen generates large, filled-out ears, making this the highest-yielding type.
If the nitrogen requirements of the High Yield x Southern hybrid are not met, the plant cannibalizes the nitrogen in the stalk and lower leaves. This causes the early death of the corn plant, which leads to stalk rot and lodged corn.
On highly productive soils, plant populations of 34,000 plants per acre are required before Eastern genetic types can generate their optimal yield potential. High soil fertility, nitrogen for yield and potassium for stalk quality are required to support plant populations at this high density.
When population is adjusted downward, Western genetic types are tolerant to lower nitrogen. However, they are sensitive to low potassium. Western genetics do well where native soil potassium levels are high, such as western Iowa, northeastern Nebraska and southeastern South Dakota. In fact, high potassium levels in the plant drive drought tolerance in Western types.
Potassium is important in plant water management because it regulates the opening and closing of the stomata. By increasing the speed at which they open and close the stomata, Westerns lose less moisture via evapotranspiration and improve water-use efficiency and drought tolerance.
This can take place because it flexes its ear and allows a reduction in plant population. The tolerance to lower fertility cannot be captured unless populations are reduced.
This type makes tall, leafy hybrids, which respond well to the higher fertility levels required for creating a larger photosynthetic factory. With high fertility, these large plants can drive yield, but low fertility results in a cannibalization of the stalk to fill the ear, causing root lodging during harvest.