Effect of Temperature and Moisture on Aminocyclopyrachlor Soil Half-Life

Aminocydopyrachlor will control a variety of invasive weeds but may injure sensitive plant species if seeded into treated soil too soon after application. Aminocyclopyrachlor 50% dissipation time (DT50) ranged from 3 to > 112 d in four soils from the Northern Great Plains. The DT50 was dependent on several factors including soil type, moisture content, and temperature. Across four different soil textures, aminocyclopyrachlor dissipation generally increased as soil moisture content increased, but moisture had less of an impact in sandy soils. Aminocyclopyrachlor dissipation also increased as temperature increased in the four soils. The most rapid dissipation occurred in soils with higher clay content, which also had the highest organic matter content of the soils evaluated, and an average DT50 of less than 20 d. Seeding sensitive pasture, range, or crop species after aminocyclopyrachlor applications should be done with caution since the herbicide has potential for long persistence in the soil.