About 60 percent of Arkansas production is still dryland, and that's why University of Arkansas researchers continue to seek ways to increase dryland yields and lower production costs.

For the second year, the Arkansas Soybean Promotion Board has funded research studies of deep tillage, one-pass (low input) production and moisture conservation in dryland fields. A team led by research agronomist Dr. Terry Keisling is doing the work.

The team also includes Dr. Lanny Ashlock, Cooperative Extension Service soybean specialist; Dr. Ford Baldwin, Extension weed scientist; Dr. Dick Oliver, research weed scientist; Dr. Larry Purcell, soybean physiologist; and Dr. Carl Dillon, a farm management economist.

"We're looking at the influence of deep tillage on heavy clay and silt loam soils in the Delta," said Keisling. "The deep tillage work on clay soils is being done at the university's Northeast Research and Extension Center at Keiser and on two farmers' fields in Lee County.

"The work on silt loam soils is being done at the UofA Pine Tree Branch Station in St. Francis County and on three farm fields in Lee County."

Keisling said deep tillage on heavy clay soils generated yield responses of 5 to 12 bushels per acre. "In one case, we had a response of 16 bushels."

He said deep tillage on silt loam soils produced no yield response in either 1995 or 1996.

"We also looked at different tillage tools, including a v-ripper; a Paratil by Tye, which has the action of moldboard plow except it doesn't turn the soil over; and a DMI Ecolo-Tiger, which is a hyperbolic subsoiler with a wide point," said Keisling.

"The v-ripper, with hyperbolic subsoil shanks, appeared to be the most effective.

"We also looked at the interaction of deep tillage and acid-tolerant soybean varieties on silt loam soil. The idea here is that if an acid subsoil and a tillage pan prevent root growth, then you might get a response by using deep tillage and an acid-tolerant soybean variety.

"We didn't."

This year, Keisling initiated a study to compare deep tillage with chemicals for control of perennial weeds such as red-vine and big-root morningglory.

"It would be nice if we could deep till and get a 10 to 12 bushel increase and at the same time control weeds," said the researcher.

Another part of Keisling's dryland research was an examination of low input production. "Using an air seeder, we field cultivated, planted and incorporated the herbicide all in one trip," he said.

The one-pass approach was compared to a no-till approach using a burndown herbicide, a conventional row system and a broadcast system where the seed is incorporated with a disc and a do-all.

"The results in 1995 were that as long as we got a stand of beans, the yields were about the same for all of these approaches," said Keisling. "The yields were in the 40-bushel range for all of the full season beans.

"This year at Keiser, yields are about the same for all the approaches--in the 50-bushel range. If there is one system that's better, it's the disk and do-all approach."

Doublecropped yields were also about the same for the different tillage and seeding systems--in the 20-bushel range.

Keisling's other dryland study looks at how soil moisture is affected by different planting dates and approaches to seedbed preparation, including no-till with a chemical weed burndown, shallow cultivation with a field cultivator, and allowing weeds to grow 4-6 inches high and then disking them under, which many farmers do.

"When you plant early in the season, it doesn't matter which type of seedbed prep you use because the soil profile is full of water from winter storage," noted Keisling. "As you move into mid-May plantings, the more effect the type of seedbed preparation has on the soil moisture level."

Which approach is best?

According to Keisling, shallow, 1-inch to 1.5-inch, cultivation with a field cultivator conserves the most moisture, followed by no-till with the chemical weed burndown and, finally, waiting until weeds are 4-6 inches high and disking them under.

"We planted our dryland beans in April, mid-May, mid-June and mid-July," he said. "The July planting was too late. April-planted beans on Grand Prairie-type soil gave us problems, too. Extensive periods of rainfall into May caused severe stand losses.

"When you plant early in soil with poor surface draining, you're going to have problems."

Keisling said economic analyses are underway for each farming practice studied in the dryland research project.

"The bottom line is profits."