Dissipation of the Herbicides Atrazine and Alachlor in a Maryland Corn Field

Abstract

Atrazine and alachlor are commonly used in Maryland corn fields (Zea mays L.), primarily as pre‐emergence herbicides. This research was part of a watershed program designed to monitor nonpoint source pollution due to runoff of chemicals from agricultural lands. Atrazne (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) and alachlor (2‐chloro‐2′,6′‐diethyl‐N‐methoxymethyl acetanilide) were sprayed on a corn field at rates of 1.7 kg/ha and 2.3 kg/ha, respectively. Soil cores were taken from sites at four elevations in the field. At the highest elevation, atrazine underwent a decrease in the surface 5‐cm layer, but a fraction of atrazine was leached into the deeper soil profile. At the middle altitude, atrazine concentrations in the 2.5‐ to 30‐cm soil profile changed very little during the growing season. At the lowest elevation, where soil moisture was rather high, atrazine had an even distribution in the soil profile. Thus, the data on field soil indicated both downward and lateral movement of atrazine. Alachlor remained in the top 8 cm of the soil. Low teachability of alachlor in field soil is believed to result from a strong affinity of alachlor molecules for soil organic matter. Runoff losses were detected at a weir situated near the bottom of the drainage channel of the watershed. During the 1976 growing season, 17 g/ha of atrazine and 3.6 g/ha of alachlor were discharged. About 60% of the discharged herbicides were in the dissolved phase. Flow‐weighted mean herbicide concentrations in the runoff water were 16.9 µg/liter (atrazine) and 0.6 µg/liter (alachlor). Atrazine carryover detected in the corn field soils was generally from 0.09 to 0.56 µg/g. Between 5 and 13% of the atrazine applied to the fields was estimated to be carried over to the next growing season.

Atrazine and Alachlor Inputs to Surface and Ground Waters in Irrigated Corn Cultivation Areas of Castilla-Leon Region, Spain

“…This again reveals the parallel transport of both herbicides to surface waters. This parallel distribution of atrazine and alachlor in surface waters has also been reported by other investigators (Wu, 1980;Kimbrough and Litke, 1996).…”

“…This will give rise to a delay in borehole atrazine loading with respect to alachlor. In comparative studies performed on field plots and soil columns, other authors (Wu, 1980;Funari et al, 1998) have also shown that alachlor is washed out faster than atrazine.…”

“…Comparative studies addressing the persistence of alachlor and atrazine in the soil (Wu, 1980;Helling et al, 1988;Bowman, 1990;Wietersen et al, 1993;Funari et al, 1998) have shown that alachlor is much less persistent than atrazine. Nevertheless, although the dynamic of atrazine and alachlor in the soil has been studied sufficiently, and the results pointing to the difficulty for both compounds to reach ground waters, their presence there is a fact.…”

Impact of rainfall and tillage systems on off‐site herbicide movement

“…Baker et al (1978), reported greater alachlor and cyanazine [2-[[4-chloro-6-(ethylamino)-l,3,5-triazin-2-yl]amino]-2-methylpropanenitrile] runoff losses in sandy loam than in silt loam soil, indicating that soil texture influences herbicide movement. Wu (1980) and Wu et al (1983) compared runoff loss of alachlor and atrazine 3,, and found total losses of alachlor were much less than that for atrazine. Increasing the amount of atrazine applied increases loss, but does not affect the percentage loss as compared to the applied concentration (Hall et al, 1972).…”

Hydrogeochemistry and Groundwater Quality Assessment of Lower Part of the Ponnaiyar River Basin, Cuddalore District, South India

“…Hydrogeochemical study is a useful tool to identify these processes that are responsible for groundwater chemistry. Several authors have reported about the presence of contaminants in soils (Muir & Baker, 1978;Wu, 1980) and waters (Kolpin, Barbash, & Gillion, 1998) in various part of the globe and also in India (Elango, Kannan, & Senthil Kumar, 2003;Srinivasa Rao, Reddy, & Nayudu, 1997;Subba Rao, Gurunadha Rao, & Gupta, 1998). Contamination of the groundwater by domestic, industrial effluents and agricultural activity is a serious problem faced by developing countries.…”