Influence of soil texture and tillage on herbicide transport
ABSTRACT Two long-term no-till corn production studies, representing different soil texture, consistently showed higher leaching of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] to groundwater in a silt loam soil than in a sandy loam soil. A laboratory leaching study was initiated using intact soil cores from the two sites to determine whether the soil texture could account for the observed differences. Six intact soil cores (16 cm dia by 20 cm high) were collected from a four-year old no-till corn plots at each of the two locations (ca. 25 km apart). All cores were mounted in funnels and the saturated hydraulic conductivity (Ksat) was measured. Three cores (from each soil texture) with the lowest Ksat were mixed and repacked. All cores were surface treated with [ring−14C] atrazine, subjected to simulated rainfall at a constant intensity until nearly 3 pore volume of leachate was collected and analyzed for a total of . On an average, nearly 40% more of atrazine was leached through the intact silt loam than the sandy loam soil cores. For both the intact and repacked cores, the initial atrazine leaching rates were higher in the silt loam than the sandy loam soils, indicating that macropore flow was a more prominent mechanism for atrazine leaching in the silt loam soil. A predominance of macropore flow in the silt loam soil, possibly due to greater aggregate stability, may account for the observed leaching patterns for both field and laboratory studies.
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ABSTRACT: Soil residues of atrazine, alachlor, and cyanazine were measured in no-till corn plots that had received annual herbicide applications from 1981–1985. Treatments were as paired combinations of herbicides at recommended rates. Three cores were collected from 3–4 replicated plots per treatment; sampling occurred late in 1983, then periodically during the growing season in 1984 and 1985. Persistence up to 6 weeks after herbicide application was in the order: atrazine > cyanazine > alachlor. Sampling after ca. 6 weeks gave the order atrazine > alachlor > cyanazine. Atrazine and alachlor were found to the lowest sampled depths in 1983 (1–1.5 m) and 1984 (0.4–0.5 m). Cyanazine was not detected below 0.3 m. In 1985, atrazine leached to ≥0.3–0.5 m by 40 days, but no subsoil residue was detected at 139 days. Alachlor and cyanazine had virtually disappeared by 40 days.Chemosphere 01/1988; 17(1):175-187. · 3.14 Impact Factor
- Journal of Environmental Quality - J ENVIRON QUAL. 01/1993; 22(4).
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ABSTRACT: Recent laboratory studies have shown that starch-encapsulation (SE) may reduce leachate losses of certain pesticides. This study compares field-scale mobility and persistence of SE-atrazine [2-chloro-4-ethylamino-6-isopropylamino-s-triazine] and alachlor [2-chloro-N(2,6 diethylphenyl)-N-(methoxymethyl)acetamide] to that of a commerciall formulation (CF) of atrazine and alachlor. The research site consisted of four (0.25 ha) fields. Two fields were under no-tillage management (NT) and two were under conventional tillage (CT). One field in each tillage system received SE-formulated atritzine and alachlor, while the others received CF-atrazine and alachlor. Chemical movement and persistence was determined by analysis of surface samples (â¼3 cm) taken immediately after application and 1.1-m soil cores collected seven times over 2 yr. No significant difference in herbicide residue levels was observed between NT and CT, but there was a herbicide formulation effect. Soil residue analysis suggests that SE-atrazine was more persistent and less mobile than CF-atrazine. Starch- encapsulated-alachlor was slightly more persistent than CF-alachlor, but no differences in mobility between formulations was observed. The differential field behavior between SE-herbicides is attributed to the faster release of alachlor from the starch granules. Increased atrazine persistence was attributed to the reduction of leachate losses. The reduction in atrazine leaching is likely due to the slow release from the starch granules and subsequent diffusion into the son matrix where it is less subject to preferential flow processes. 20 refs., 6 figs., 1 tab.Journal of Environmental Quality - J ENVIRON QUAL. 01/1994; 23(2):355-359.