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Rains Create Management Decisions For Corn Producers

By Kay Ledbetter

Rain is a double-edged sword right now for agricultural producers, especially corn producers, according to Texas A&M AgriLife Extension Service personnel in Amarillo.

“It’s important for producers to realize that they still have options for corn as we move into June,” said Dr. Jourdan Bell, AgriLife Extension agronomist. “While we are seeing delays in corn planting, the greater concern at this time is for those producers with saturated soils and corn in the ground.”


Flooded fields have keep farmers from planting, or could be causing damage to seed already planted, according to Texas A&M AgriLife Extension Service specialists. (Texas A&M AgriLife Extension Service photo by Kay Ledbetter)

Flooded fields have kept farmers from planting, or could be causing damage to seed already planted, according to Texas A&M AgriLife Extension Service specialists.

Bell said some corn producers who do not have seed in the ground are beginning to get concerned, but there is still time and producers should not rush planting in non-ideal conditions.

“Previous research has demonstrated that good yields can be obtained with late May and even early June plantings,” she said. “Moving the planting date later in the season actually pushes the critical growth stage of tasseling, which coincides with the period of greatest water demand, out of the hottest part of the summer.”

Research by Dr. Qingwu Xue, Texas A&M AgriLife Research plant physiologist in Amarillo, evaluated four planting dates – May 15, June 1, June 15, July 1 – and six hybrids of three maturity classes. There was not a significant yield decrease by moving the planting date out of April into late May, according to Xue’s results. He achieved 200-bushel yields even with 115-day hybrids planted in late May and early June.

“Of course, as we move later, we may need to adjust the maturity class shorter than a 115-day hybrid,” Bell said. “While longer season hybrids have a greater yield potential, they also have a greater water requirement, so producers have the potential to save a few inches of irrigation water, which translates to reduced pumping costs. Dr. Xue’s work demonstrated up to a 5-inch reduction in crop water use.

“If we consider the cost of water and current corn prices, it is possible that a slight reduction in yield as a result of switching the hybrid maturity class may not necessarily result in less profit at current prices,” she said.

However, Dr. Ron French, AgriLife Extension plant pathologist in Amarillo,  said, “Late-planted corn is more susceptible to fungal diseases because plants are younger when fungal activity increases, plant tissue is softer and thinner for easier fungal penetration, and rapid fungal growth will lead to a higher fungal population.

“Therefore, a good corn hybrid with good disease resistance may be desirable under late-planting and humid conditions.”

French said corn is more prone to seed and seedling diseases when soils are cool, 50-55 degrees, and poorly drained. Other factors that might affect disease severity may include seed quality, whether seed was treated with a fungicide, genetic resistance and the cropping history of that field.

“Some of the most common seedling diseases are caused by soilborne fungi such as fusarium and rhizoctonia, but also by the water-mold pythium, and potentially, plant parasitic nematodes,” he said. “Other fungi have also been associated with seedling damping-off, blight or wilt and may cause diseases such as Aspergillus or Nigrospora seedling blight and Anthracnose leaf blight.”

Seedling diseases may look similar to one another and could be mistaken for herbicide damage, insect damage or stresses, French said. Delayed emergence and low seedling counts may indicate that seedling diseases may be occurring.

“Seed may be rotted even before germination, seedlings may emerge but then collapse, which is an indication of post-emergence damping-off, or seedlings may rot prior to emergence, which is an indication of pre-emergence damping-off,” he said.

French said if a field has a history of seedling diseases in the past few years, some management strategies to consider are: crop rotation, better drainage, seed treated with one or more fungicides and/or a nematicide, and planting when soil temperatures are warmer than 55 degrees.

Bell said the much-needed rain received in the past month has delayed much of the area’s corn planting, however, there was a window last week when producers were out planting.

“Now with this most recent set of storms, some with 4 inches of rain, and the cooler temperatures, there is a lot of corn that has not germinated. As a result, we have seed in the ground under saturated conditions.”

Under these conditions, the cell membrane can be damaged, leaving the seed and seedling susceptible to fungal diseases that French discussed, she said.

Flooding also results in anaerobic conditions, Bell said. Oxygen deprivation kills the cells and reduces the metabolic rate, which also leaves the seed and seedling more susceptible to disease pressure.

“We have to remember that flooding doesn’t only mean ponded water in the fields,” she said. “Super-saturated fields will also have this problem; fields with heavy clay and fields that don’t drain will definitely be an issue.

“It only takes four days for the seed to sit in saturated conditions for us to start seeing degradation, causing either variable emergence that will affect the yields at the end of the season or even seed rot.”

Soil crusting is another issue that can follow heavy rains and warm temperatures, which speed up drying, Bell said.

“I expect we will see producers out with rotary hoes in the next few weeks, but crop injury from the rotary hoe is also a concern,” she said. “In addition to soil crusting, compaction is another consideration. As producers rush to get back in the field, it is always important to be mindful that compaction is greater with increased soil moisture.”

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