July 12, 2002

5 Min Read

As more and more cotton farmers try no-till, they're finding there's a lot more to the practice than simply burning down the winter weeds, dropping a no-till planter into the old beds and planting.

Researchers at the Louisiana State University AgCenter say their research shows that optimum fertilizer rates for no-till can vary significantly, depending on the tillage system and the presence or absence of different cover crops.

They're also saying that growers might need to be a little patient when launching into no-till.

“In the first few years the yields for no-till and conventional tillage were about the same,” said Don Boquet, an agronomist at the LSU Macon Ridge Branch Research Station near Winnsboro, La. “Then, the no-till cotton produced higher yields than cotton in the surface till treatments.”

Speaking at the Northeast Research Station Field Day at St. Joseph, La., Boquet discussed the results of an 11-year study comparing no-till and surface till planting systems; hairy vetch, wheat and native vegetation for cover crops; and five nitrogen rates — 0, 35, 70, 105 and 140 pounds per acre.

In the first four years, 1990 through 1994, cotton lint yields were similar for the two tillage regimes — no-till and surface till, said Boquet. Longer term, in years five through 11, the no-till yields were higher.

“Although yield increases from no-till practices were only 9 percent greater than with surface till, economic analyses demonstrated that no-till benefits were augmented by lower production costs than surface till,” he noted.

No-till cotton behind a hairy vetch cover crop produced the highest yields for either of the two tillage systems — 1, 271 pounds in the no-till and 1,296 in the surface till — but with different nitrogen rates.

The 1,271-pound yield with 70 pounds of fertilizer N behind vetch in no-till was only 28 pounds higher than the 1,243-pound yield produced with 35 pounds of N, which was only 5 pounds higher than the yield produced with 0 N. Applying 105 and 140 pounds of N on the vetch cover crop plots decreased yields.

“The optimal N rate varied with tillage and cover crop and was 0 pounds per acre following vetch, 70 to 105 pounds per acre following native cover and 105 pounds per acre following wheat cover,” said Boquet. “These results demonstrate that the recommended fertilizer N rate should be specific for each tillage and cover crop regime.”

Boquet was speaking on the site of a 21-year rotation study, comparing the benefits of planting cotton, corn, soybeans, grain sorghum and wheat rather than continuous cropping of one of the commodities.

“When we began this study, it had been in continuous cotton for many years,” he said. “After the first year of corn, we increased cotton yields 15 percent. Today, when we plant cotton behind one year of corn, we increase yields 15 percent.”

The researchers observed increases of 5 to 10 bushels in soybean yields in the rotational study at first, but, in recent years, they have been producing 20 bushels more per acre in the rotation than in continuous soybeans. They also saw no increase in corn yields the first 10 years, but now are harvesting 20 to 30 bushels more corn in the rotational plots.

“Corn and soybeans seem to receive the most benefits from rotation, but other crops might offer higher prices,” said Boquet. “All the rotations seem to have about the same benefit for cotton, so you should pick the crop that offers the best return that year.”

Steve Moore, an agronomist at the LSU AgCenter's Dean Lee Research Station near Alexandria, La., said Louisiana corn growers are watching their crop closely because of the hot, dry weather corn plants have been enduring. Their main concern: Aflatoxin.

USDA estimates that Louisiana farmers planted 500,000 acres of corn, a nearly 60 percent increase above the 315,000 acres they planted in 2001. Those 500,000 acres would be the largest corn crop in Louisiana since 1998.

Aflatoxin is caused by a fungus, aspergillus flavis, which cannot form until the corn starts forming kernels. It needs a combination of hot and dry weather to attack, according to Moore.

“Just watch the weather,” he said. “If the temperature gets above 95 degrees and the rain shuts off, you may need to start looking out for aflatoxin.”

Aflatoxin was a disaster for the state's corn crop in 1998, Moore said. So the LSU AgCenter started a breeding program in 1999 to find a strain that is resistant to aflatoxin. Researchers will get that program's “report card” later this year and will be able to see if they are on the road to developing more resistant hybrids, he said.

In other comments at the field day, LSU AgCenter Chancellor Bill Richardson thanked farmers for their support of the AgCenter's efforts to win an increase in its budget in the Louisiana General Assembly.

The Assembly, which concluded its session the day before the field day on June 13, passed new taxes that will provide much-needed raises for LSU AgCenter faculty and staff and additional funding for LSU's research and Extension programs, he said.

“I know that many of you have called your legislators and asked them to support the increased funding, and I want you to know that all of us in the AgCenter appreciate your help,” he said. He also commented on the AgCenter's services to farmers.

“What we have here today is a cadre of LSU AgCenter personnel from all over the state who are trained in many different areas to bring you the information you need,” Richardson said of the faculty members who spoke during field tours. “This is what we had in mind when we started reorganizing the AgCenter four years ago.

“We have combined the research stations and the Cooperative Extension Service offices and formed eight regions all over the state. We're trying to do everything we can to better serve the needs of the residents of Louisiana.”

A Denise Coolman of the LSU Extension Service contributed to this story.

e-mail: [email protected]

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