March 25, 2002
Growing dryland corn in Georgia always involves a certain amount of risk, dependent as it is on weather conditions. But by following a few best management practices, dryland growers can decrease their risk and get the highest potential return when there’s plenty of rainfall during the season.
Forty to 45 percent of Georgia’s corn acreage remains in dryland situations, says Dewey Lee, University of Georgia Extension agronomist. "This past year, rainfall helped to propel the state to a record average yield of 123 bushels per acre — about 16 bushels per acre more than the previous record," he says.
Another reason for the record yield, he adds, is that more corn acres have been shifted to irrigated ground as the total corn acreage has shrunk.
"We’ve always focused a tremendous amount of our work on research on irrigated corn because of the increased yield potential. Inputs are higher in irrigated corn, but the potential return also is greater," says Lee.
To get a better idea of the best management practices for dryland corn production, Lee looked at the practices of past winners of Georgia’s dryland production efficiency contest.
"Looking back over the past 10 years, the most efficient dryland growers are early adopters of practices that have been proven by research. They are on the cutting edge of this research," says Lee.
It is very difficult, he says, to grow dryland corn in some of the soils found in Georgia. "But we obviously have some very good dryland growers. They have refined their programs so that when they plant corn, they know their best chance of getting rainfall will be during the silking period. They look at previous history, and they match the silking period of a certain hybrid to the time during which they stand a greater chance of receiving rainfall.
"Growers in the eastern part of the state are planting corn about one month later than in southwest Georgia because their best chance of rain comes about 30 days later. Those growers utilize the eastern winds for rainfall, particularly if a hurricane passes through."
It’s becoming more difficult, says Lee, for Georgia corn producers to fulfill the quality expectations of the market. The collapse of the hog market has hurt Georgia growers, and the poultry industry has used aflatoxin as an excuse not to buy Georgia corn, he says.
"This is doubly so for dryland growers. If a dryland grower has aflatoxin, it’s certainly higher than it would be for an irrigated producer. It’s very difficult to fulfill the expectations of customers. This leaves the dryland grower on the margins, and they’re very narrow margins."
Weather patterns, says Lee, also have affected dryland corn production in Georgia. "We now see more rainfall in our winter months than in our summer months, and this has had an impact on dryland production."
Dryland growers need to know, he says, if their soils are capable of sustaining profitable yields with current rainfall patterns. Some soils, such as the heavy-textured ones found in north Georgia, are more efficient at holding moisture than the sandier soils of southwest Georgia.
Dryland growers also must know, he continues, which inputs are necessary for achieving maximum profits. "If you spend too much, cost-per-bushel will rise to unprofitable levels. If you don’t have enough inputs, and you do get rainfall, you won’t maximize your inputs or your production. The idea is to keep your profits up and your costs down."
An important consideration in dryland production, says Lee, is hybrid selection. One helpful tool in this process, he adds, is the University of Georgia hybrid evaluation manual.
"Data is compiled from each hybrid tested this past year, and it gives you a picture of how stable that hybrid is in a dryland or irrigated environment. It’s always best if you use two or three hybrids that show good stability.
"In other words, they may not be the highest yielding hybrids in the test, but they’re always better than the average, and that’s what you want. You want a hybrid that, in extreme environments, has demonstrated genetic stability. Such a hybrid will produce more yields — year in and year out — than the top yielding hybrid from previous years’ tests in one location."
Growers also need to stay informed about the advantages and disadvantages of using new genetic technology, says Lee. It’s important to consider the extra cost of new technology, and whether the extra cost will pay off in the long run, he adds.
Seeds or kernels planted per acre is another important consideration, he says. Research has shown that 16,000 to 18,000 seeds per acre is sufficient in sandy loam soils.
"If you have slightly heavier-textured soils, 18,000 to 20,000 kernels is an excellent target to shoot for in dryland production. In the heavy-textured soils of north Georgia, you can go slightly higher, to the 20,000 to 24,000 range. You won’t be hurt as badly if you don’t receive enough moisture because of the ability of these soils to hold water."
Soil preparation research from the past five years has shown that no-till systems work well in heavier soils, notes Lee. "Our most successful growers, for the most part, are no-till growers. Our high-residue, conservation tillage research in Plains and Tifton shows not yield response to deep tillage in heavy soils. If you can get equal yields in a no-till situation, it’s worth the savings in energy and other costs.
"And if it’s available, growers should use residue with in-row subsoiling. Some of our farmers have adopted closing furrows with wheel compression rather than using the baskets seen in strip-till environments. When we use wheel compression to close the furrow, the residue is closer to the row and provides better protection for the soil."
Turning to fertility, dryland growers should apply phosphorus, potassium and magnesium according to soil test values, says Lee, with yield goals in light soils of 100 to 140 pounds per bushel.
"Nitrogen needs to be applied at one to 1.2 pounds per bushel yield goal. If you have a 100-bushel yield goal, 120 pounds of nitrogen should be sufficient. If you’re in very light soils, you might want to go with 1.3 pounds."
It also works well, he says, if a grower can utilize a legume in his rotation. An example would be following soybeans in north or east Georgia.
Poultry litter also can be beneficial in a dryland situation, says Lee. "You need to look at how to best utilize poultry litter in a whole farm system. Once it’s applied to corn, it will have an effect on peanuts or cotton, particularly if it goes out with micronutrients. When we make a decision on corn, we’re making a decision for the whole farm system."
Research has shown that in a whole farm system with cotton, peanuts and corn, two tons of litter per acre is sufficient for maximizing the nutrients and for being a good steward of the environment, says Lee.
"If you’re not growing crops such as peanuts, then you can increase the amount, up to about four tons. With four tons of litter, we can meet all of the nitrogen needs of the corn crop. This works especially well in a dryland environment."
Another option to consider in dryland production is narrow row widths, says Lee. "Peanuts and cotton demand that your rows be 36 to 38 inches. But if you’re able to go into another cropping system, such as soybeans in north Georgia, there’s a benefit - particularly in dryland corn — in squeezing that row width down to 30 inches.
"Recent work in North Carolina, South Carolina and Georgia has demonstrated the even more narrow rows — such as 20, 18 or 15 — benefit corn and soybeans. As we narrow the rows, we spread the seed over more land mass. We can increase our seeding rate slightly and, with good rainfall, we’ll get a higher plant population."
Narrow rows also do a better job of weed compression and water utilization than wider rows, he adds.
Lee suggests that dryland producers avoid planting corn in areas with heavy grass pressure from weed pests such as Texas panicum and Johnsongrass. They’re some of the most difficult to control, he says, and they require more expensive herbicides.
"The Liberty Link and Roundup Ready hybrids offer a new tool for corn growers, particularly in narrow rows. These traits are being placed in hybrids that are better adapted to our area. If not this year, then in the next couple of years we’ll be able to better adapt that technology because it’ll give us a more total control program for weeds such as Texas panicum and Johnsongrass."
If you’re not already using a directed spray rig, it’s a good option, says Lee, for weed emergencies.
"It’s not such an expensive option, and the products we can apply directly are relatively inexpensive and do a fine job with good management."
Lee advises dryland corn producers not to use an insecticide unless it’s absolutely necessary. The only way to use insecticides efficiently, he says, is to scout and spray at threshold levels.
"It’s also important that we plan ahead and harvest early. Most growers have a difficult time doing this because they don’t have a batch dryer. This one area — getting the crop out early — is a real weakness in our program.
"When we do get the crop out early, we avoid field losses and late weed infestations, such as those from morningglories. I’d suggest you begin harvesting at 22 to 24 percent moisture, in dryland or irrigated fields. Harvesting early also reduces your risk of aflatoxin."
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