Movement of pesticides under two irrigation regimes applied to turfgrass

Current public concern has focused attention on the environmental effects of chemical applications to turfgrass areas. Our objective was to investigate the movement of isazofos ({O-[5-chloro-1-(1-methylethyl)-1H-1,2,4-triazol-3-yl]O, O-diethyl phosphorothioate}), chlorpyrifos {[0,0-diethyl-0-(3,5,6-trichloro-2-pyridnyl) phosphorothioate]}, metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl) alanine methylester], and pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] when applied to Kentucky bluegrass turf established on 50-cm long and 20-cm diameter undisturbed soil columns of Nicollet (fine-loamy, mixed, mesic Aquic Hapludolls) in which the macropore system remained intact. This study was conducted for 28 d and used a heavy (four, 2.54-cm applications) and a light (16, 0.64-cm applications) irrigation regime. Average isazofos, chlorpyrifos, metalaxyl, and pendimethalin recovered (by extraction) from soil columns under the heavy irrigation regime, plus that collected in the leachate, were 8.8, 11.5, 23.8, and 7.9%, respectively. Isazofos, chlorpyrifos, metalaxyl, and pendimethalin recovery from soil columns under the light irrigation regime, plus that collected in the leachate, averaged 3.4, 6.6, 13.9, and 4.6%, respectively. On average, 6.3, 0.5, 7.7, and 0.2% of the applied isazofos, chlorpyrifos, metalaxyl, and pendimethalin, respectively, were measured in leachate from soil columns under heavy irrigation in contrast to 0.4, 0.0, 0.2, and 0.0%, respectively, from soil columns under light irrigation. Comparing the four applied pesticides, metalaxyl is most likely to be leached because of a low soil sorption, followed by isazofos, pendimethalin, and chlorpyrifos. Metalaxyl was found in the highest percentage in the leachate followed by isazofos, pendimethalin, and chlorpyrifos. From this research, we conclude that irrigation practices (frequency and depth of application) can have an impact on the movement of pesticides through soil profiles.