MISSISSIPPI STATE -- No-till cotton farming has gained in popularity in recent years as farmers are learning it can be a successful practice when managed correctly.

Dr. Jac Varco, agronomist with the Mississippi Agricultural and Forestry Experiment Station, said no-tillage cotton increased from 1,183 acres in 1989 to 52,146 acres in 1997. Starting with the 1985 Farm Bill, farmers are required to put highly erodible land in either the Conservation Reserve Program or use conservation practices on that land.

"With producers having to reduce erosion losses, they're turning to conservation tillage practices, and no-tillage is the strictest form of conservation tillage," Varco said. "With no- tillage, there is no disturbance of the soil other than to plant the seeds in the ground."

Dr. Larry Oldham, Extension soil specialist, said conservation tillage does more than prevent soil erosion.

"With conservation tillage, organic matter increases in the soil," Oldham said. "This improves properties of the soil such as the particles' ability to stick together, water infiltration and nutrient-holding power. It also improves the soil's ability to store air and water."

Farmers use herbicides to control the vegetative cover and weeds in no-till farming, and at least 30 percent of the ground is covered by crop residues. With conventional farming, producers add organic matter such as crop residues, animal manure and gin trash, but tilling in the warm, humid Mississippi climate speeds the breakdown of these.

"It's very difficult to build organic matter in the soil with conventional tillage systems," Oldham said.

While conservation tillage increases the amount of organic matter in the soil, it changes fertilizer needs. Varco conducted a study of cotton's nitrogen needs and how to best satisfy requirements for no-tillage cotton farming.

"Nitrogen dynamics change when you switch from conventional tillage to no-tillage," Varco said. "The presence of crop residues left on the soil surface alters the amount of nitrogen needed and the way it should be applied."

For seven years, Varco studied sources of nitrogen, amounts needed for no-till cotton and ways to apply it.

"We had no data on which to base recommendations for no-tillage cotton," Varco said.

Varco found nitrogen was most efficient when broadcast on the soil surface as ammonium nitrate. This worked better than urea- ammonium nitrate solutions banded below the surface or dribbled on the surface. It also out-performed urea broadcast on the surface.

"The results show that no-tillage cotton can be successful in the long run," Varco said. "Even considering the cost of the individual fertilizers, ammonium nitrate has been shown to be economical when used on no-till cotton."