Persistence and leaching of C-14-metribuzin -dimethyl)-3-(methylthio)-
1,2,4-triazin-5(4H)-one] and metabolites were determined in Tanana (lo
amy, mixed, nonacid Pergelic Cryaquept) and Beales (sandy, mixed Typic
Cryochrept) silt loam soils under irrigated potato (Solanum tuberosum
L.) and dryland barley (Hordeum vulgare L.) conditions in the subarct
ic. Overall, dissipation of total C-14 (metribuzin and metabolites) wa
s significantly slower (P > 0.05) in Tanana than Beales soil over the
first 105 d, but by 468 d, the C-14 remaining (51% of applied) did not
differ (0.05 < P) between soils. Initial degradation of metribuzin wa
s rapid in both soils but was not significantly different between soil
s (0.05 < P). At 35 d after application 24% of applied metribuzin rema
ined, At the end of the study (468 d), 5.0% of the applied metribuzin
was still present. Unextractable residues accounted for the greatest a
mount of C-14 remaining in the soils. of the extractable metabolites,
greater amounts of desaminometribuzin were found in both soils than di
ketometribuzin or desaminodiketometribuzin. More water moved through t
he irrigated than nonirrigated soil as evidenced by bromide movement.
Also, more C-14 moved to 15 to 22.5 cm depth in the irrigated than in
the nonirrigated soil, but < 1% of applied C-14 was detected below 22.
5 cm for both soils and irrigation treatments. Rapid metribuzin degrad
ation in combination with sorption processes minimized leaching of tot
al metribuzin residues through these subarctic surface soils.