MOVEMENT OF PESTICIDES UNDER 2 IRRIGATION REGIMES APPLIED TO TURFGRASS

Current public concern has focused attention on the environmental effe cts of chemical applications to turfgrass areas. Our objective was to investigate the movement of isazofos -chloro-1-(1-methylethyl)-1H-1,2, 4-triazol-3-yl]O, O-diethyl phosphorothioate}), chlorpyrifos {[0,0-die thyl-0-(3,5,6-trichloro-2-pyridnyl) phosphorothioate]}, metalaxyl [N-( 2,6-dimethylphenyl)-N-(methoxyacetyl) alanine methylester], and pendim ethalin -ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] when applie d to Kentucky bluegrass turf established on 50-cm long and 20-cm diame ter undisturbed soil columns of Nicollet (fine-loamy, mixed, mesic Aqu ic Hapludolls) in which the macropore system remained intact. This stu dy 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 is azofos, chlorpyrifos, metalaxyl, and pendimethalin recovered (by extra ction) from soil columns under the heavy irrigation regime, plus that collected in the leachate, were 8.8, 11.5, 23.8, and 7.9%, respectivel y. 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 ave rage, 6.3, 0.5, 7.7, and 0.2% of the applied isazofos, chlorpyrifos, m etalaxyl, and pendimethalin, respectively, were measured in leachate f rom soil columns under heavy irrigation in contrast to 0.4, 0.0, 0.2, and 0.0%, respectively, from soil columns under light irrigation. Comp aring the four applied pesticides, metalaxyl is most likely to be leac hed because of a low soil sorption, followed by isazofos, pendimethali n, and chlorpyrifos. Metalaxyl was found in the highest percentage in the leachate followed by isazofos, pendimethalin, and chlorpyrifos. Fr om this research, we conclude that irrigation practices (frequency and depth of application) can have an impact on the movement of pesticide s through soil profiles.