Experiments were conducted in a growth chamber to study alachlor and metolachlor metabolism in soil and corn and to determine if alachlor and metolachlor and their metabolites are exuded from corn roots to the growth medium. Alachlor was more readily absorbed by corn than was metolachlor. The absorption of alachlor and metolachlor was 72 and 55%, respectively, 10 d after seedling emergence (DAE). Alachlor and metolachlor were rapidly metabolized in corn, although metabolism rates were higher with metolachlor than with alachlor. Ten similar alachlor metabolites were detected in roots and shoots. In addition, two metabolites were detected only in the shoots, and one metabolite was detected only in the roots. Metolachlor metabolism in corn produced fewer metabolites than did alachlor metabolism. At 5 DAE, 10 and 9 metabolites were detected in shoots and roots, respectively. The metabolism of alachlor and metolachlor in soil showed patterns similar to the metabolism in corn but produced fewer metabolites. One unique alachlor metabolite appeared in soil but not in corn. Roots of corn seedlings treated with 14C-alachlor or 14C-metolachlor released significant amounts of radioactivity to the surrounding growth medium 5 d after treatment. Plants treated with alachlor released more radioactivity than did plants treated with metolachlor.
Nomenclature: Alachlor; metolachlor; corn, Zea mays ‘Patriot 6168’.