Leaching and runoff losses of the postemergence-applied herbicide dicamba w
ere evaluated over a 3-yr period (1989 to 1991). Dicamba was applied at the
recommended rate (0.56 kg ai/ha) to conventional and mulch tillage planted
corn fields on Hagerstown silty clay loam (fine, mixed, mesic Typic Haplud
alf). Mulch tillage followed several years of no-tillage corn. Root zone le
achates were collected utilizing pan lysimeters placed 1.2 m below the soil
surface. Surface runoff was monitored and collected with an HS-flume and a
utomated sampling equipment. Leaching was greatest during 1989, and runoff
events were recorded only during this season. Leachate samples containing m
easurable levels of dicamba were obtained within 21 d of herbicide applicat
ion or within slightly more than one soil half-life of this chemical. More
dicamba leached under mulch tillage than conventional tillage management. T
illage rotation (no tillage to mulch tillage) did not alter the leaching lo
ss potential of dicamba beneath the minimally tilled soil surface, as postu
lated, compared with the previous untilled surface. The mulch tillage surfa
ce reduced runoff water losses compared with conventional tillage, but earl
y-season leaching activity, coupled with the minimal persistence of dicamba
in soil, negated runoff transport of this herbicide from either tillage sy
stem when the first runoff event occurred 12 d after its application.