Cg. Cogger et al., TRANSPORT AND PERSISTENCE OF PESTICIDES IN ALLUVIAL SOILS - I - SIMAZINE, Journal of environmental quality, 27(3), 1998, pp. 543-550
Pesticide leaching is a concern in the alluvial valleys of western Was
hington, where high-value crops are grown in soils with water tables <
3 m deep. We conducted this project to determine the longterm leaching
pattern of simazine [2-chloro-4,6-bis-(ethylamino)-s-triazine] applie
d to red raspberry (Rubus idaeus L.) and strawberry (Fragaria x ananas
sa Duch.). Simazine was applied to strawberry and raspberry in paired
plots at two sites. Strawberry received a split application (total 2.2
kg ha(-1)) in August and November, and raspberry received a single 4.
5 kg ha(-1) application in November. We applied simazine yearly from 1
986 to 1989, and sampled soil (to 180 cm) and shallow groundwater mont
hly until April 1991, and at one site again in 1994. Most of the simaz
ine remained in the surface 15 cm of the soil or degraded, but small a
mounts moved downward. Preferential flow soon after application was no
t the main cause of downward movement. Simazine was persistent, with d
isappearance half lives of 128 and 175 d at the two sites the first ye
ar. Some simazine remained in the soil 4 yr after the final applicatio
n. Simazine was most mobile beneath raspberry at one site. This site h
ad finer texture and slightly more organic matter, but a lower K-d for
simazine than the other site. Small amounts of simazine reached shall
ow groundwater beneath both crops. The observed simazine leaching peak
was more asymmetric than the peak predicted by the PRZM-2 model, an i
ndication of nonequilibrium adsorption-desorption effects on simazine
movement.