Residual and contact herbicide transport through field lysimeters via preferential flow

• Published in: Journal of environmental quality 2004-11, Vol.33 (6), p.2141-2148
• Main Authors: Malone, R.W, Shipitalo, M.J, Wauchope, R.D, Sumner, H
• Format: Article
• Language: English
• Subjects: Adsorption; agricultural runoff; Agronomy. Soil science and plant productions; Alachlor; Analysis; Applied sciences; Atrazine; Biological and medical sciences; Contaminants; corn; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental impact; Environmental Monitoring; Environmental perception; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; glufosinate; Glycine max; glyphosate; Herbicides; Herbicides - analysis; Herbicides - chemistry; infiltration (hydrology); Leaching; linuron; Lysimeters; metribuzin; pesticide residues; Pollution; Pollution, environment geology; Preferential flow; Rainfall; Soil; Soil Pollutants - analysis; Soil sciences; soil transport processes; sorption; Soybeans; Water Movements; Water Pollutants, Chemical - analysis; water pollution; Zea mays
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2004.2141

Usage of glyphosate [N-(phosphonomethyl)-glycine] and glufosinate [2-amino-4-(hydroxy-methylphosphinyl)butanoic acid] may reduce the environmental impact of agriculture because they are more strongly sorbed to soil and may be less toxic than many of the residual herbicides they replace. Preferential flow complicates the picture, because due to this process, even strongly sorbed chemicals can move quickly to ground water. Therefore, four monolith lysimeters (8.1 m2 by 2.4 m deep) were used to investigate leaching of contact and residual herbicides under a worst-case scenario. Glufosinate, atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide], and linuron (3-3,4-dichlorophenyl-1-methoxy-1-methylurea) were applied in 1999 before corn (Zea mays L.) planting and glyphosate, alachlor, and metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] were applied in 2000 before soybean [Glycine max (L.) Merr.] planting. A high-intensity rainfall was applied shortly after herbicide application both years. Most alachlor, metribuzin, atrazine, and linuron losses occurred within 1.1 d of rainfall initiation and the peak concentration of the herbicides coincided (within 0.1 d of rainfall initiation in 2000). More of the applied metribuzin leached compared with alachlor during the first 1.1 d after rainfall initiation (2.2% vs. 0.035%, P < 0.05). In 1999, 10 of 24 discrete samples contained atrazine above the maximum contaminant level (atrazine maximum contaminant level [MCL] = 3 microgram L(-1)) while only one discrete sample contained glufosinate (19 microgram L(-1), estimated MCL = 150 microgram L(-1)). The results indicate that because of preferential flow, the breakthrough time of herbicides was independent of their sorptive properties but the transport amount was dependent on the herbicide properties. Even with preferential flow, glyphosate and glufosinate were not transported to 2.4 m at concentrations approaching environmental concern.