ADSORPTION AND RELATIVE MOBILITY OF FLUMETSULAM

Laboratory studies were conducted to evaluate flumetsulam adsorption a nd mobility in seven Mississippi soils of different organic matter con tent, pH, and texture. Adsorption isotherms were determined for all so ils using a 1:1 (soil:water) technique. In six of seven soils, Freundl ich n constants were close to unity, suggesting a partitioning-like ad sorption mechanism for flumetsulam. Mobility was examined using packed soil columns. C-14-flumetsulam recoveries in leachate ranged from 1 t o 70% and were influenced by both organic matter content and soil pH. However, the effects of organic matter content and soil pH were not in dependent. Consequently, clear relationships between flumetsulam mobil ity and either organic matter content or soil pH were not established across all soils. However, among soils of similar pH (7.5 +/- 0.3), mo bility decreased linearly (R-2 = 0.75) as organic matter content incre ased from 0.7 to 3.6%. Across soils with similar organic matter conten t (3.9 +/- 0.3%), mobility increased linearly (R-2 = 0.98) as soil pH increased from 5.3 to 7.2. Net adsorption constants (K-d) provided a m ore accurate assessment of flumetsulam mobility across all soils than K-oc.