Failed wheat acres due to drought and late season freezing weather presents farmers with options for planting these acres to cotton, according to J.C. Banks, Oklahoma State University Extension state cotton specialist.

Speaking at a recent cotton production meeting at the Southwest Oklahoma Research and Extension Center at Altus, Okla., Banks said farmers should consider several points in replanting decisions.

First, farmers should check with local Farm Services Agency offices on rules for planting cotton behind failed wheat. These rules are complicated if insurance has been paid on the failed wheat.

Herbicides are another concern.

"Be aware of herbicides used in wheat weed control for the past two years," he said. "Some products have a 25 month rotation back to a broad leaf plant like cotton. Soil pH is important since carryover of some products is influenced by soil pH. Information is on the product label.

“Soil analysis for herbicides is expensive and takes a long time. The best way to test for presence of a carryover herbicide is to plant cotton in a small area and observe it for injury symptoms.

"Most of the common wheat herbicides that carry over will not affect germination of the cotton, but will start to show up on the first true leaves above the cotyledon leaves. Cotton injury symptoms for most commonly used wheat herbicides are a light green or pea green leaf color in the terminal of the plant, with some pink or red showing up on the veins on the leaf."

Banks said chances of producing a good cotton crop are greatly enhanced if subsoil moisture is replenished.

"At this time," he said, "we have had a very dry fall and winter and both topsoil and subsoil moisture are extremely low. We need at least five or six inches of rainfall to allow it to soak in instead of runoff. Planting on surface moisture alone is risky."

If wheat had ample fertilizer or if it was top dressed, more fertilizer for cotton will likely not be needed. If the wheat acreage has been well fertilized for several years, he said, there might be enough nitrogen available below the normal rooting area of the wheat to support cotton late in the season.

"Cotton has a tap root and will utilize deep nitrogen that is unavailable to wheat," he said. "It is better to soil test. A one bale per acre cotton crop will need about 60 pounds of actual nitrogen available. If the wheat has been well fertilized, phosphorus and potassium will probably be adequate."

To plant cotton behind failed wheat, Banks recommends a glyphosate herbicide to kill the wheat as soon as possible. In order to conserve soil moisture, he cautioned against chiseling or disking the ground to prepare the soil surface to plant cotton.

"This will dry out the soil to the depth of the plow layer," he said. "With our limited ground cover, the cotton planter will likely not need to be modified with no-till attachments. Either plant without disturbing the soil or use the front disks on the planter to clear out an area for the seedbed."

Banks said Roundup can provide weed control throughout the growing season on Roundup Ready Flex cotton. If annual weeds and grasses are a problem, Prowl H20 can be tank mixed with the Roundup in the pre-emergence or the early post emergence stage of the cotton, he said.