Test-plot studies on runoff of sulfonamides from manured soils after sprinkler irrigation.

Three test-plot series have been performed to gather information on runoff of sulfonamides from manured arable and grassland after sprinkler irrigation. To prepare test slurries with defined aged residues, liquid bovine manure was fortified with sulfadiazine, sulfadimidine, and sulfamethoxazole and stored short-term. After test-slurry application, the arable land was treated by soil cultivation before irrigation, and the manured grassland was irrigated directly with 50 mm h(-1) for 2 h. The runoff suspensions were sampled at 5- to 10-min intervals, separated into aqueous phase and suspended matter and residue analyzed. Higher runoff emissions were found from manured grassland plots. The discharge volumes ranged from 106 to 252 L and the total runoff emissions ranged from 13 to 28% of sulfonamides applied initially. Within the first 20 min of the irrigation period that represented a rainfall of 17 mm, emissions, on average, were 4%. The loads of sulfonamides predominantly occurred in the runoff water. The only emissions via suspended matter, on average, were 0.02%. On arable land, however, the runoff was reduced by soil cultivation. Discharge volumes and sulfonamide emissions were 36 to 128 L and 0.1 to 2.5%, respectively. Despite the high-intensity sprinkler irrigation, major emissions did not occur until a 60-min delay.