Effect of Soil Texture and Soil pH on Amicarbazone Persistence

Amicarbazone is a photosystem II-inhibiting herbicide utilized for weed species in turfgrasses. Amicarbazone is highly water soluble, has a low soil organic carbon–water partition coefficient, and does not dissociate. Although previous research suggests that amicarbazone persistence may range widely, it has been reported to be very short in acidic soils and moderately persistent in alkaline soils. Laboratory experiments were completed to evaluate the effect of soil pH on amicarbazone persistence and sorption in Drummer loam, Lubbock sandy loam, and Cecil sandy clay loam soils. Amended and unamended soils were included within each experiment for comparison. Amicarbazone persistence ranged widely (9–117 d) due to soil texture and pH and was more persistent under alkaline soil conditions. Under acidic conditions, amicarbazone was more persistent in loam and sandy loam (half-life, T_1/2 = 57 d) compared with sandy clay loam (T_1/2 = 9 d), while less difference was noted under alkaline conditions. Calculated sorption coefficients were comparable, suggesting that persistence across soil textures and pH is not solely due to differential sorption. Turfgrass managers should be cognizant of soil pH and texture, as they may affect persistence and bioavailability, thereby influencing turfgrass tolerance.