"We've had much success with narrow-row soybeans, and we've been looking at narrow-row corn since 1996," says Frederick. "It has potential, but there are pros and cons."
Reviewing the benefits of narrow-row corn, Frederick says it offers faster canopy closure, aiding in protecting the soil and in blocking out weeds. It also makes the soil temperature cooler, thereby making the plants cooler.
"We're also seeing better wildlife habitats with narrow-row corn production," he says. "When those leaves canopy over, they protect quail from the hawks above."
Higher yields, adds Frederick, are another proven benefit of narrow-row corn. "But narrow rows are not a stand-alone practice. It's a good practice, but it doesn't stand on its own. Conservation-tillage fits in very well with narrow-row corn production, and the benefits are similar.
You should be able to put these two practices together to make the benefits of each more efficient," he says.
Conservation-tillage also protects the soil, promotes higher yields and improves wildlife habitat, so it's a natural fit with narrow-row
production, says Frederick.
"Another component that fits well in this system is transgenic technology, such as Roundup Ready and Liberty Link. You need this broad spectrum weed control when you can't cultivate, and this goes for conservation-tillage and narrow rows," he says.
Precision nutrient application also fits in well with the narrow-row/conservation-tillage concept, he continues. "Phosphorus always stays near the surface in conservation-tillage systems. So, precision application will fit in well with conservation-tillage systems that also utilize narrow rows," says Frederick.
Numerous tests have been conducted in South Carolina, he says, comparing the yields of narrow-row versus conventional-row corn production. The narrow rows are 15 inches while the conventional rows are 30 inches. The tests also looked at disking versus no-till, and the no-till system including deep tillage.
The yields, says Frederick, were higher for 15 inches versus 30 inches.
Yields also were higher in no-till versus disking.
"The no-till, narrow row and deep tillage are cumulative effects in these tests."
Small-plot work using conservation-tillage with a Para-Till also showed a yield advantage with the more innovate systems, he adds. "Yield advantages ranged from 8 percent to 70 percent. But realistically speaking, we're probably seeing a yield advantage of 10 to 20 percent."
Researchers also are looking at the narrow-row/conservation-tillage system across the various soil types found in the Coastal Plain, says Frederick.
"There are at least half a dozen soil types in some of our fields, and nothing behaves the same over those different soil types. We wanted to see how narrow-row conservation-tillage stacked up against conventional systems across different types of soil. In most cases, narrow-row/conservation-tillage had the higher yields.
"One area where we don't see much of a response is in wetter soils. It's not so much the narrow rows as it is the conservation-tillage and deep-tillage that don't respond as well in wet soils. These practices normally get more water to the plant. So, if soils are wet to begin with, the effects will be less."
In most narrow-row systems, seeding rates are being increased by about 15 percent, says Frederick. "More plants will mean more water use, especially during the growing season. If you experience drought conditions throughout the season, narrow-row systems will be the first to use the water, so you'll have lower yields in a narrow-row system under extreme drought conditions."
Deep-tillage is an important component, especially in South Carolina, because of the prevalence of hardpan layers in the soil, he says.
"If you look across the South, you see a lot of reports that show narrow-row systems losing yield to 30-inch systems. We also lost yield where we didn't include deep-tillage in the system. Including deep-tillage as part of the package helps to insure a yield increase."
Farmers are using several methods to break up soils, says Frederick, with the Para-Till and DMI systems being two of the most common ones.
"Some farmers start out with Para-Till, switch to DMI and come back to Para-Till. I think the jury still is out on which one of these work the best. You tend to have a softer soil surface with the Para-Till and a firmer one with DMI."
Research has proven, says Frederick, that conservation-tillage systems increase water infiltration. In a three-year test, the water run-off from a conventional system was 2.4 inches in one year compared to essentially no run-off from the conservation-tillage system.
"More water coming off the traditional system means that more sediment and nutrients are coming off. Water retention is a big benefit of these innovative systems. More water in the field means more water for the plants."
The narrow-row/conservation-tillage systems offer "free" weed control, says Frederick. "Canopy closure is much faster in narrow-row production, shading out the weeds. Tests have shown about two-thirds less sicklepod in a narrow-row versus a traditional system and practically no crabgrass in a narrow-row system."
Looking at phosphorus levels following corn harvest, Frederick says there is much less phosphorus in-row than in the row middles in conservation-tillage systems. The reason for this, he says, is because there are more roots in the row in conservation-tillage.
"It's the complete opposite with potassium, with more in the row than in the row middles. The reason for this is that there is a good amount of potassium left in the stalk, and it leaches into the row. This tells us that if we pull a soil sample from the row, we'll under-estimate on phosphorus and over-estimate on potassium. If you're pulling soil samples, take some in the row and out in the row middles."
Even though nitrogen leaching probably is less in narrow-row systems because of the close proximity of the plants, such a system probably will take up more nitrogen because there's better root distribution across the
soil, he says.
Sulfur deficiencies are common in narrow-row systems, says Frederick, and the current recommendation calls for 1 pound of sulfur for every 10 to 15 pounds of nitrogen.
"When harvesting narrow-row corn, you must slow down, and you'll still lose some corn. Harvesting these systems is a learning process, and it'll take time."
Although transgenic varieties fit in well with the narrow-row/conservation-tillage systems, growers might not want to spend the extra money for the technology because weed control is so good in these systems, says Frederick.
"If you put out a good burndown, and a good residual at planting, you might not have to come back over the top, especially if you began with clean fields." e-mail: email@example.com