By Kay Ledbetter
While producers cannot control the environment during the growing season, they can control the agronomics and irrigation, said Dr. Jourdan Bell, Texas A&M AgriLife Extension Service agronomist in Amarillo.
Bell, speaking at the High Plains Irrigation Conference and Trade Show recently, said good irrigation will not compensate for bad agronomic management practices, and vice versa.
“In corn, irrigation scheduling is necessary to supplement the seasonal water demands of the crop because in-season precipitation is generally not sufficient to meet the crop water requirement on the Texas High Plains,” she said.
Corn ear response to two different in-season irrigation treatments.
“While crop water use is driven by environmental demands, agronomic management can also affect water management,” Bell said. “It is important producers realize there is a synergy between agronomics and irrigation to reach yield goals. Efficient water use equals yield, and yield equals money.”
Bell outlined a list of corn hybrid characteristics that producers should consider.
Crop water use can be maximized with hybrid selections, she said. Knowledge of the hybrid characteristics offered, such as maturity, drought tolerance, ear flex, leaf orientation and “stay-green” are important.
Bell said Dr. Qingwu Xue, a Texas A&M AgriLife Research crop stress physiologist in Amarillo, studied drought-tolerant hybrids using three different irrigation regimes. He determined that 30 inches of seasonal crop water use is about the maximum needed.
“He started seeing the yields decline after that,” she said, adding some producers trying to get maximum yields may be over-watering.
Bell said with traditional hybrids, as water-use decreases, yield decreases. The drought-tolerant hybrids, however, seem to partition the water more efficiently and yields do not decrease as rapidly.
Heat tolerance is another hybrid trait producers should be aware of, she said. Heat tolerance in corn is not the same as drought tolerance. High temperatures can damage exposed silks and pollen.
While pollen shed occurs in the morning naturally allowing the plant to escape high daytime heat, there are still specific hybrids better suited to areas with higher morning temperatures, Bell said.
“Even across the Panhandle, we normally see up to 10 degrees differences in morning temperatures that can affect fertilization,” she said. “This can be managed with hybrid selection and planting date.”
Corn hybrids also offer three ear traits – fixed ear, semi-flex ear and flex ear – which reference ear size, Bell said. Ear flex or size can affect yield and can be detrimental, if the right one for the management practices is not selected.
Fixed-ear corn kernel numbers will remain fairly stable, but it allows the producer to plant at a higher population to optimize yield, she said. Semi-flex ear maintains the ear size in high populations and can flex up or get bigger to preserve yields at lower populations. The flex ear offers producers the ability to flex according to in-season growing conditions and inputs.
“However,” Bell warned, “this is where producers can get in trouble if they try to plant high populations. They could end up with small ears when they flex the wrong way due to competition for resources.”
She said the leaf orientation trait can also be important according to a producer’s management practices. An upright leaf will maximize high population, while a pendulum hybrid will have a canopy that closes much earlier to minimize soil moisture evaporation. The semi-upright leaf provides the best of both worlds, allowing sunlight to penetrate the canopy. This can be important for a producer depending on population and row spacing.
It’s also important for producers to manage their stay-green traits, she said. Stay-green allows the plant to continue to photosynthesize under drought, but it also enhances deeper kernel set, longer duration of grain filling and a better test weight.
“But in order to get the most of the stay-green trait, you have to manage nitrogen,” Bell said. “Green leaves need nitrogen.”
She advised that while some producers put all their nitrogen up front, they might want to reconsider.
“In 2015, we saw many fields that had received 8-plus inches of early season rain and nitrogen was pushed below the root zone,” Bell said.
Optimally, a producer might consider splitting their fertilizer three or four ways, she said. A post-tassel fertilizer application around the blister stage allows for the plant to stay green, which increases kernel set and yield.
“If you have the ‘racehorse’ environment – plenty of water and fertile soil – then you are able to push populations with a fixed ear hybrid,” she said. “If you are in a drought environment, select a pendulum-leaf type to enhance canopy closure and minimize evaporative losses from the soil, and then plant lower populations in order to use flex-ear hybrids to maximize yields. With variable soils, you might want a semi-upright leaf and semi-flex ear.”
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