A study by the University of Arkansas indicates that shifting from 38-inch rows to twin-row, 15-inch or to twin-row, 7.5-inch configurations in cotton won’t negatively impact lint yield and quality.

According to Tom Barber, Extension cotton specialist at the University of Arkansas, the study’s findings could be useful for cotton producers who’ve shifted to twin-row corn and soybeans and want to do the same for cotton. Doing so could simplify field operations, allowing the same planting equipment to be used across crops.

“Our crop mix has changed,” Barber said. “We have a lot of farmers growing cotton, corn and soybeans, and there are lot more corn and soybeans than cotton. With the high costs of seed and technology fees, many farmers are wondering if there are ways to cut back on equipment and use one planter for everything. So we’re trying to find ways to use similar equipment for all three crops.”

The study on the effect of row configuration and seeding rate on cotton yield and fiber quality was conducted in 2007 and 2008 on clay soils at the Northeast Research and Extension Center in Keiser, Ark., and on silt loams soils at the Lon Mann Cotton Research Station in Marianna, Ark. NREC director Fred Bourland and NREC agronomist Daniel Stephenson also participated in the study.

The cotton variety ST 4554B2RF was planted at both locations for both years of the study. Scientists constructed 38-inch beds on which all of the configurations were planted. They planted single 38-inch rows, twin 7.5-inch rows, and twin 15-inch rows. Plant populations ranged from 35,000 plants per acre to 75,000 plants per acre.

Researchers planted standard 38-inch and twin-row 15-inch configurations with a John Deere vacuum planter and the 7.5-inch twin rows with a Monosem twin-row planter.

With 7.5-inch twin rows, there was a 30.5-inch middle and a 23-inch middle on the twin-row 15-inch rows. Barber said the 15-inch twin-row cotton rows were located too close to the edge of the bed and would have worked better with at least a 40-inch bed. “The top of the bed needs to be about 20 inches across. You could knock it down and plant, but we used a hipper/roller to roll it and flatten the bed out.”

Data was gathered on stand counts, plant mapping data, lint yield and fiber quality. Plants at both research stations were furrow irrigated.

A John Deere picker with heads designed specifically for 15-inch picking was used to pick the 15-inch plots. The 38-inch rows and the 7.5-inch twin rows were picked with a standard picker configured for 38-inch rows.”

Over the two years of the study, researchers did not notice significant differences between the planting patterns for plant height, nodes above white flower, turnout, lint percent or fiber quality.

The only plot showing significant differences from other plots in terms of the number of fruiting branches were 7.5-inch twin rows on silt loam at the Marianna location. “When we looked at seeding rate across locations, we saw more fruiting branches at the lower seeding rate. We didn’t see any differences in the number of vegetative branches between the patterns.”

While there were no significant yield differences between planting patterns, researchers did pick up on a few trends. On the Keiser clay soil, “as you move the rows in from 38 inches, you’re going to see a higher yield. On the Marianna silt loam soil, which is our better cotton ground, there is usually not much difference in any of the patterns. Most of the time, the narrow rows are usually lower in yield. There’s a reason why we’ve been growing cotton on 38-inch rows in the Delta.”

Barber said boll mapping showed more fruit on the 7.5-inch cotton. “However, because of where the fruit was — lower on the stalk — and the configuration of the plants, and the way both plants came into a single 38-inch picking unit, we just couldn’t get them effectively picked.”

None of the seeding rates provided a decided advantage for the three planting patterns. Researchers did see significant differences in plant survival by seeding rates. “We were getting close to 100 percent survival until we planted 65,000 to 75,000 plants per acre, where we were only getting 70 percent to 80 percent survival.”

As seeding rate increased on clay soils, “we saw a trend for increasing yields. On silt loam soils, if you get a good stand, the low seeding rate is going to be just about as good as anything else. Getting a good stand is the key.”

For 38-inch rows, there was no ideal seeding rate, according to the study. “But on 7.5-inch twin rows, there is a slight increase in yield as we increase seeding rate.”

Barber says twin-row 15-inch cotton “is going to be better on our mixed soil and clay soil ground.”

Barber says the two years of the study indicate that twin-row 7.5-inch cotton will deliver good yields. “Using a twin-row system means they only have to change the planter and nothing else. If I’m a corn, soybean and cotton farmer, I can use the same machinery and plant them all.”

On the other hand, harvest efficiency of twin-row 7.-5 inch cotton “is going to become a problem depending on how your picker is set up.”

UA researchers plan to continue the study in 2009.

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