Mark Maier thought he probably hadn’t seen the last of the barnyardgrass he was spraying in a rice field near Stuttgart, Ark., last year.

Maier, a field representative for Jimmy Sanders Inc., in Stuttgart, had applied one-half ounce of Regiment plus Dyne-A-Pak at 2 percent on some larger barnyardgrass and expected to follow that with another one-half ounce of Regiment post-flood.

“When we came back to look at the treatment, all of the barnyardgrass was dead, and that included some large grass,” said Maier. “We had a lot of dry conditions last year, and I didn’t expect it to work that well.”

In spraying bispyribac or Regiment and Dyne-A-Pak, Maier learned what a number of researchers and crop consultants are beginning to find: Regiment and UAN (Dyne-A-Pak contains UAN) at 1 percent to 2 percent can provide much more satisfactory grass control than Regiment alone.

“It makes a whole new chemical out of the Regiment,” says Maier. “Adding the adjuvant and UAN made me feel a lot more at ease in recommending Regiment. We were able to kill 10-inch tall, tillering grass with a regular rate of Regiment.”

“You need to think of it like biscuits and gravy,” says Frank Carey, field market development specialist for Valent U.S.A. Corp., the company that markets Regiment. “You shouldn’t have one without the other.”

Carey and other Valent crop specialists say UAN, a urea-ammonium nitrate solution that contains either 28 percent or 32 percent nitrogen, is helping change growers’ perception of the herbicide.

“Four years ago, we were applying Regiment on dry soils – clay soils so dry they had cracked open – and it flopped,” said Carey. “Last year, we tried it on dry soils again, and it worked. The difference was applying it with UAN.”

Maier agrees that the addition of UAN to the tank mix appears to make the weed control from Regiment more reliable than with Regiment and an adjuvant.

“It takes out the inconsistency,” he said. “You put in UAN, an adjuvant – we used Dyne-A-Pak but any good adjuvant will work – and coverage, and it is going to kill the barnyardgrass.”

Adding UAN wasn’t a shot in the dark, according to Cam Smith, market segment manager for Southern row crops for Valent U.S.A. The combination of Regiment, UAN and a surfactant was based on research using Carbon 14 Regiment by Dan Reynolds, professor of weed science at Mississippi State University.

Studies conducted by Reynolds and Joe Massey, an assistant professor in the Plant and Soil Sciences Department at Mississippi State, found that the addition of UAN and a methylated vegetable oil (Dyne-Amic) significantly increased the absorption rate of the Carbon 14 Regiment in barnyardgrass.

Field testing by Charles Guy, a researcher with G&H Associates in Tillar, Ark., in 2004 appeared to bear out the results of the Carbon 14 studies.

“Our field market development specialists took the concept to fields in each of the rice-growing states last year, and they found the same thing,” said Smith. “One of them, Andrew Duff, told us ‘You have to see it to believe it.’”

As a result of the research and the field trials, Valent has issued a product bulletin that lists 10 surfactants approved for use with Regiment: Cadence from MFA; Dyne-Amic from Helena Chemical Co.; Dyne-A-Pak, Helena; Freeway, United Agri-Products, Inc.; Kinetic HV, Helena; Regiwet, Jimmy Sanders; Rivet, Agriliance, LLC; Silkin, Agriliance; Soysurf Plus, Jimmy Sanders; and Syl-tac, Wilbur-Ellis Co.

“The addition of 2 percent volume/volume 32 percent or 28 percent UAN to one of the above listed surfactant (except Dyne-A-Pak) is recommended and may enhance the activity of Regiment when applied under some conditions,” the bulletin says.

“UAN is not a substitute for an approved adjuvant, but rather should be used in combination with one of the approved adjuvants. (The adjuvants Phase II from UAP and Soysurf Extra from Jimmy Sanders also contain UAN.)

Valent is also recommending the addition of UAN and a methylated seed oil/silicone adjuvant with tank mixes of Regiment and Permit.