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Prepare for planting corn, sorghum

Last year, a good farmer in the corn verification trials got about 60 cents more per bushel by using a telephone and checking prices, says Arkansas Extension corn specialist William Johnson.

“He was offered $1.80 per bushel from an elevator. After calling around, he found a catfish food mill that paid him $2.50. That's a vivid example of why farmers should call around and check the prices,” Johnson told those attending the Arkansas Agricultural Expo in Forrest City on Feb. 7.

“Check all options in marketing your crop. A lot of guys, with an LDP, have been making $2.20 per bushel corn. But there are plenty of others who have been forward contracting with feed mills and have been at over $3 corn.”

Looking at weed control in corn, one of the biggest problems Arkansas corn farmers see is broadleaf signalgrass. There are several approaches to this weed. Many farmers use a Dual/Frontier/Lasso to control the signalgrass and then come back with a post-application of atrazine, says Johnson.

“There are times we run into yellow nutsedge. Permit has been phenomenal in controlling that weed. When we run into yellow nutsedge we use about a half ounce of Permit along with some Basis Gold.”

Corn fertility

“On nitrogen, we're looking at 1.2 units per bushel of grain. So with a yield of 150 bushels, about 180 units of nitrogen are needed in a split application. We like to put out about a third to half of our nitrogen pre-plant incorporated. In that system, about 60 pounds are given in the first dose. You come back with 120 units in the four to six-leaf stage,” says Johnson.

Nitrogen given at tasseling happens if Johnson runs into a situation where the yield is running in the 200 bushel range. Such a field may need 240 units.

“If we have good water, good weather and everything is going well, we'll go ahead and put out the other shot of nitrogen right before tasseling.”

Sulfur nutrition in corn is akin to the same in wheat, says Johnson. If a field has a deficiency, about 50 to 100 pounds of ammonium sulfate needs to be put out. Normally the deficiencies will occur where there are sand-blows.

“In terms of nutrients, I've seen many zinc problems in the state. Any time you have a pH above 6.5 and there's rice rotation going on, there will be a zinc deficiency in corn. We are seeing more of this in fields that are pH 7 that don't have rice on them. But if you're in this situation, you need to be putting out about 10 pounds of actual zinc (in a zinc sulfate form) or a chelated zinc at a pound.”

Many growers put out the chelated zinc with their atrazine, says Johnson. By doing that the plant takes the zinc up directly and corn is “very forgiving when it is below six-leaf stage. Anytime it's over the six-leaf stage, the plant is setting a lot of yield potential.”


Some big impacts have been seen with Bt hybrids, says Johnson. Last year, at the Cotton Branch Experiment Station there was an 8 to 10 bushel increase in the April plantings with Bt hybrids. In May plantings, researchers saw some 30 to 50 bushel yield increases versus non-Bt hybrids.

“Corn borers at third generation migrate down into the root wads. That's why we encourage — once picking has occurred — that farmers work the field up and expose the borers to the cold weather. You need to let the weather take them out.”

“Irrigation is essential in corn production — not only for high yields but also to reduce aflatoxin risk.”

Johnson and colleagues used to go by black-layer when determining cessation of irrigation. Once black-layer was found, the farmers stopped irrigating. But there were complaints about cutting ruts in the field, says Johnson.

“Sure, we're not going to have a lot of water taken up into the plant when it's black-layer because it's physically mature. It takes a while for the soil to dry out.

“So what we've gone to is pulling a lot of ears and breaking them in half. We then look at the kernels and slice them up. When the kernel's starch layer has moved to 50 percent and there's good moisture, no more irrigation is needed. If we find the starch layer has moved 50 percent down and the soil is crusted and dry, you need one more irrigation.”

Grain sorghum

Over the last four years Johnson has had only a couple of sorghum meetings. This year, he's already attended seven.

“That tells me there's some big interest in this crop because a lot of soybeans have burned up the last couple of summers.”

In the last two years, Arkansas has had sorghum producers making 5,000- to 6,000-pound yields consistently.

“There's a lot more money in that than in 8-bushel soybeans,” says Johnson.

A key advantage of sorghum is its drought tolerance. The crop is also good for reducing nematodes — reniform, cyst or root-knot, it doesn't matter.

“Soil organic matter is also increased by growing grain sorghum. We've burned up our soils lately and sorghum will help with that. Also, sorghum will help with other crops' yields because we're breaking the disease triangle by growing it.”

Planting dates are much more critical in sorghum than corn, says Johnson.

“In corn, we're looking at 55 degrees at 2 inches of depth at 9 a.m. With grain sorghum, it's 65 degrees. The seed is much smaller and has more of a tendency to rot than does corn.

“If you've got 60-degree soil at 2 inches and a forecast of warm, sunny days, that's probably okay to plant. Twenty to 30 days after the last killing frost is another way to go. But in eastern and northern Arkansas, you're usually looking at March 20 as being the target date.”

If farmers remember nothing else, Johnson says, they should remember seeding rates for sorghum. Failure to abide by rates is the biggest problem he runs into. Seeds range from 12,000 seeds per pound all the way to 18,000.

Johnson says farmers should want 50,000 plants per non-irrigated acre with a yield potential of 4,000 to 5,000 pounds. If a grower is looking at better soils, he may go to 60,000 plants per acre. On irrigated cotton soils, some 75,000 plants per acre may be planted.

“Typically, problems arise when we plant about 100,000 plants per acre. That means lodging and disease troubles. It's very critical that growers know how their planters are distributing seed. With planting, 20-inch or 30-inch rows are best. Planting depths are best at 1 to 1.5 inches. This is critical because all the rooting activity will occur from the seed to the soil surface until the plant is knee-high.”

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