Jc. Clausen et al., PAIRED WATERSHED COMPARISON OF TILLAGE EFFECTS ON RUNOFF, SEDIMENT, AND PESTICIDE LOSSES, Journal of environmental quality, 25(5), 1996, pp. 1000-1007
A paired watershed study was used to compare runoff, sediment, atrazin
e (2-chloro-4-ethylamino-6-isopropylamino-1,3,5 triazine), and cyanazi
ne loro-6-(ethylamino)-S-triazin-2-yl]amino]-2-methyl propionitrile) l
osses from conventional-tilled (CT) and reduced-tilled (RT) corn (Zea
mays L.) watersheds. During a 13-mo calibration period both watersheds
were moldboard plowed and runoff was measured in H-flumes. Composite
samples were analyzed for sediment and for atrazine and cyanazine in d
issolved and sediment phases. During a 30-mo treatment period, one wat
ershed was moldboard plowed while the other was disk harrowed. Reduced
tillage decreased runoff by 64% and sediment losses by 99% but did no
t change dissolved atrazine or cyanazine concentrations in runoff. Con
centrations of sediment-sorbed pesticides increased in runoff. The RT
reduced mass losses of atrazine and cyanazine in runoff, primarily bec
ause of decreases in runoff volume and sediment mass. Most pesticide l
osses occurred within 3 wk of field application. Pesticide loss was pr
imarily in the dissolved phase. The paired watershed approach was a us
eful technique for determining watershed treatment effects when differ
ences existed between watersheds chosen for study.