L. Masse et al., TILE EFFLUENT QUALITY AND CHEMICAL LOSSES UNDER CONVENTIONAL AND NO-TILLAGE .2. ATRAZINE AND METOLACHLOR, Transactions of the ASAE, 39(5), 1996, pp. 1673-1679
The long-term effect of no-tillage (NT) and conventional tillage (CT)
on the concentration and loss of the atrazine, deethylatrazine and met
olachlor in tile effluent was studied over a 40-month period in four l
oam soil, corn (Zea mays L.) fields of approximately 3 ha each. Atrazi
ne and deethylatrazine were detected at low concentrations in most of
the 773 samples collected between January 1991 and early May 1994. Und
er both tillage treatments, atrazine concentrations were mostly below
the USEPA advisory of 3 mu g/L while concentrations of atrazine plus d
eethylatrazine were generally below 5 mu g/L, the Canadian Interim Max
imum Acceptable Concentration (IMAC) for the sum of atrazine and its m
etabolites. Concentrations exceeding these limits were mainly observed
during rainfall-induced flow events within a few days or weeks follow
ing herbicide application. The flow-weighted average concentrations of
atrazine during flow events were significantly (p < 0.05) higher unde
r NT than CT. Metolachlor was also detected at low concentrations, and
in relatively few flow events. Concentrations were always well below
the USEPA advisory of 100 mu g/L or the Canadian IMAC of 50 mu g/L. An
nual loss of herbicides in tile effluent ranged from 0.02% to 0.34% of
the amount applied. Most loss occurred during spring flow events when
rile flow was the highest. Atrazine and deethylatrazine losses under
the NT treatment were significantly (p < 0.05) higher than those under
the CT treatment.