Can widening – or narrowing – the drill spacings help rice farmers improve their weed control? That’s a question University of Arkansas weed scientists are addressing with the help of a USDA National Institute of Food and Agriculture grant.

Besides saving on seed costs, increasing drill spacings from the standard 7.5 inches to as much as 15 inches could have an influence on weed control, according to Dr. Tommy Butts, Extension weed scientist with the University of Arkansas System Division of Agriculture.

“A 15-inch drill spacing seems pretty unheard of at this moment, although I know a couple of farmers are trying it,” said Butts, a speaker at the Arkansas Rice and Soybean Online Field Day. “But I can foresee this starting to increase in the near future with all the precision agriculture capabilities we have.”

Increased widths

Butts was describing a study at the University of Arkansas-Pine Bluff’s Small Farm Outreach Center near Lonoke, Ark., where researchers are seeding rice in row widths ranging from 5 to 15 inches, comparing several spray nozzle tips for applying herbicides and planting furrow-irrigated rice on different-sized beds.

“With vacuum planters, if we get a seed plate for it, you never know what might be possible so we wanted to investigate these different drill spacings and how that might impact our weed control,” he said.

The researchers are looking at nozzles tips that can provide very fine droplets up to ultra-coarse, very large droplets. “We’re also testing a couple of single fan nozzles versus dual fan nozzles to see if we can increase our coverage and our weed control,” he noted. “And we’re also investigating variety and hybrid impacts on these drill spacings.”

The final study involves planting furrow-irrigated rice on 30-, 38- and 60-inch beds to determine “how might that change our weed community, our weed ecosystem and our overall weed control in our rice acres.”

Mississippi State University researchers are conducting a similar study at the Delta Research and Extension Center at Stoneville, Miss.

To view the presentation, visit https://aaes.uada.edu/videos/2021-rice-weed-control/.