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In Mississippi: Fertility costs may cut corn acreage

Mississippi growers will plant “a lot less corn” this year, but cotton acres will see an increase, Extension specialists said at recent area meetings in the northwest Delta.

“High fertilizer prices will put the damper on corn plantings,” says Erick Larson, associate professor/research specialist with the Mississippi State University Extension Service.

As for cotton, Tom Barber, assistant Extension professor, plant and soil sciences, says “indications are that growers in every cotton county, except one, plan to increase acreage this year. We're looking for about 1.3 million acres, some of which I expect will be coming out of corn.”

The two met with northwest Mississippi growers recently to discuss crop prospects for this season.

With high input costs for corn — particularly for nitrogen fertilizers and seed for newer Roundup Ready varieties — growers need to tailor their programs for optimum yields, Larson says.

“Ten years ago, growers were happy if they could get 100 bushels per acre dryland, 150 irrigated. Now, they need at least 150 bushels dryland, 200 irrigated.”

Unfortunately, he says, some growers are still using 10-years-ago fertility and seeding rates. And others, while doing a good job with prescription nitrogen programs, often overlook other needed nutrients, such as phosphorus, potassium, zinc, and sulfur.

A good start is essential for top yields, he says. “Getting a good stand and adequate fertility are key factors for top yield potential, year-in and year-out.”

In a five-year study, Larson says, Mississippi research has shown the optimum nitrogen rate to be 240 pounds per acre in a split application — one-third at planting or shortly after emergence, the rest as sidedress when the plants are near waist-high and application equipment can still get through the field. “You need to be sure adequate nitrogen is there when plants enter their rapid growth stage.”

A rule of thumb, he says, is 1.3 pounds of nitrogen per bushel of yield goal.

Lodging, which can be a problem in a hurricane-beset season like 2005, can be root-caused or stalk-caused. “With stalk lodging, stalks break above ground; with root lodging, they break or pull up at the roots. Well-developed brace roots can help plants withstand root lodging.”

To encourage a good root system, Larson says, don't plant or till when soils are marginally wet; don't plant too shallow, which encourages above-ground rooting and exposes roots to hot, dry conditions and insects; control early-season insects; provide adequate fertility; and choose hybrids that performance tests have shown to have strong rooting characteristics.

“Also, the location of ears on the stalk can be a factor in lodging — the higher the ears, the more weight is concentrated in the top of the plant, making it more susceptible to lodging.”

Roundup Ready corn “really took off” with Mississippi growers last year, Larson says, with about 50 percent of acres in those varieties. While the varieties offer many advantages for weed control, he cautions that early applications are critical to reducing weed problems, and supplemental applications may be needed for broadleaf weeds, particularly morningglories.

“Be sure to heed restrictions and don't apply glyphosate to Roundup Ready corn after it's 30 inches tall. You need to hit the weeds as early as possible; once corn gets in its rapid growth phase, it can get away from you in a hurry.” If tank-mixing atrazine with Roundup, the application needs to be made when corn is 12 inches or less.

Cotton options

Ninety percent of the state's cotton crop in 2005 was Roundup Ready varieties, says Tom Barber. Only 2 percent was Liberty Link varieties and 2 percent conventional varieties.

This year, the buzz is about Roundup Ready Flex, which allows growers more weed control options.

“Flex will allow them to move out of the four-leaf window and to spray higher rates for problem weeds. It will also allow them to increase acres without increases in labor and equipment.”

It's important, Barber says, that growers “start with clean fields and stay clean.” Applications should be made as timely as possible — “and it's critical that you keep track of which fields are Flex fields, because if you spray the wrong field, you can do major damage to your crop.” Monsanto is reported to be providing flags for growers to mark Flex fields.

Barber says “it might be a good idea not to plant more than 10 percent of your crop in Flex until you get some experience with it on your farm and learn how best to manage it.”

Researchers and growers are “seeing a lot of movement from broadleaf weeds to grasses” in cotton fields, he says, and producers may need to make pre-, post-, and lay-by applications for grasses and pigweeds.

“Growers have a lot of decisions to make, and they need to do their homework in choosing varieties.”

They should look at stability and consistency of yield, he says. “And since most of our cotton now goes to the export market, quality is becoming a more important consideration.”

Growers who have a history of verticillium wilt should look for varieties that have demonstrated reduced susceptibility to the disease, Barber says. “Variety tolerance is one of the best weapons we have for this disease.”

Mississippi cotton and corn performance trials information can be found online at Click on the “Crops” link to get to the cotton and corn results.


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