Soil persistence of amicarbazone using creeping bentgrass as a bioassay

Summary

Amicarbazone herbicide is a new product in development by Arystia Lifesciences. Amicarbazone could provide extended residual control in turf due to weed root absorption. Amicarbazone is moderately persistent (reported half-lives of 15 to 87 days) in acidic and neutral soils, but breaks down slowly under alkaline conditions with pH's > 7.4. Golf courses in Georgia are highly maintained and thus this herbicide could potentially be utilized for weed control.

Situation

Recent reports indicate that amicarbazone is a photosynthesis inhibitor (PS II) and similar to atrazine with respect to spectrum and crops, although research has indicated it has greater weed efficacy at lower rates. There is very little information about the soil adsorption characteristics for amicarbazone with respect to organic matter and clay content. A major use of amicarbazone will be for the control of annual grasses in creeping bentgrass fairways. Following control of annual bluegrass large bare areas or voids will occur and creeping bentgrass will need to be re-established (seeded) in these amicarbazone-treated fairways.

Response

The effect of soil pH, clay and organic matter on seed-back intervals for creeping bentgrass following amicarbazone application. Soils were collected from various golf courses areas across the US including California, Texas, Illinois, New Jersey, Kentucky, and Georgia. These soils were analyzed for pH, sand, silt, clay, organic matter, and CEC content as well as nutrient consistency. The water holding capacity of each was also determined. Amicarbazone was soil incorporated at 0.13 and 0.26 lbs of ai/ac. Creeping bentgrass turf seed were then planted back at intervals used to determine the potential for amicarbazone injury. Seeding was conducted at 0, 10, 20, 30 and 40 days after soil treatment.

Impact

Overall this experiment would be considered the worst case scenario for amicarbazone residual activity toward bentgrass. Soils were not leached with water after planting; incubated at a cool temperature ~70 F prior to planting at 10, 20, 30, and 40 DAT, and in dark conditions. Solubility of amicarbazone is 4600 mg/L in water, indicating that in field scenarios it would most likely have some mobility into the soil profile with repeated irrigation or rainfall. Combined across incubation timings, the Georgia soil exhibited the greatest biomasses and root and shoot lengths. The CA, GA, KY, NJ, and TX soils all had a dose response when combined across incubation timings for all variables, root and shoot length and biomass. These data thus indicated that creeping bentgrass did have susceptibility at the 0.26 kg ai/ha across all incubation timings. In order of decreasing bentgrass root and shoot biomass with respect to 0.13 and 0.26 kg ai/ha: GA> NJ>KY>TX>CA>IL. It is interesting to note that for the pH's of these soils the order is similar to the shoot biomass: pH GA<NJ<KY<IL<TX<CA. For the soils with pH < 6.4 (GA, NJ, KY) the root and shoot biomass were much greater than those soils with ph >7.0 (IL, TX, CA) combined over days after treatment (DAT). Amicarbazone is moderately persistent in acidic and neutral soils, but breaks down slowly under alkaline conditions with pH's > 7.4. These data support the concept that amicarbizone is more persistent when pH was greater than 7.0 and resulted in prolonged bentgrass injury. If this herbicide is to be utilized in Georgia turf in creeping bentgrass, then applicators must know the soil pH and take care to minimize the potential for injury.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2010
• Geographic Scope: National
• County: Tift
• Program Areas:
  • Agriculture & Natural Resources