Browsing by Author "Alister, Claudio"

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    Simazine transport in undisturbed soils from a vineyard at the Casablanca valley, Chile
    (2013) Suarez Poch, Francisco; Guzman, Edwin; Munoz, Jose E.; Bachmann, Jaime; Ortiz, Cristian; Alister, Claudio; Kogan, Marcelo
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    Transport of simazine in unsaturated sandy soil and predictions of its leaching under hypothetical field conditions
    (ELSEVIER, 2007) Suarez, Francisco; Bachmann, Jaime; Munoz, Jose F.; Ortiz, Cristian; Tyler, Scott W.; Alister, Claudio; Kogan, Marcelo
    The potential contamination of groundwater by herbicides is often controlled by processes in the vadose zone, through which herbicides travel before entering groundwater. In the vadose zone, both physical and chemical processes affect the fate and transport of herbicides, therefore it is important to represent these processes by mathematical models to predict contaminant movement. To simulate the movement of simazine, a herbicide commonly used in Chilean vineyards, batch and miscible displacement column experiments were performed on a disturbed sandy soil to quantify the primary parameters and processes of simazine transport. Chloride (Cl-) was used as a non-reactive tracer, and simazine as the reactive tracer. The Hydrus-1D model was used to estimate the parameters by inversion from the breakthrough curves of the columns and to evaluate the potential groundwater contamination in a sandy soil from the Casablanca Valley, Chile. The two-site, chemical non-equilibrium model was observed to best represent the experimental results of the miscible displacement experiments in laboratory soil columns. Predictions of transport under hypothetical field conditions using the same soil from the column experiments were made for 40 years by applying herbicide during the first 20 years, and then halting the application and considering different rates of groundwater recharge. For recharge rates smaller than 84 mm year(-1), the predicted concentration of simazine at a depth of I m is below the U.S. EPA's maximum contaminant levels (4 mu g L-1). After eight years of application at a groundwater recharge rate of 180 mm year I (approximately 50% of the annual rainfall), simazine was found to reach the groundwater (located at 1 m depth) at a higher concentration (more than 40 mu g L-1) than the existing guidelines in the USA and Europe. (c) 2007 Elsevier B.V.. All rights reserved.
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    Using penoxsulam ALS inhibitor as a broad-spectrum herbicide in Chilean rice
    (2011) Kogan, Marcelo; Gomez, Patricio; Fischer, Albert; Alister, Claudio
    M. Kogan, P. Gomez, A. Fischer, and C. Alister. 2011. Using penoxsulam ALS inhibitor as a broad-spectrum herbicide in Chilean rice. Cien. Inv. Agr. 38(1): 83-93. The continuously-flooded rice production system in Chile has selected highly competitive aquatic weeds selection capable of reducing paddy yields by 25 to 50%. Penoxsulam is abroad-spectrum triazolopyrimidine (ALS inhibitor) commercially introduced in Chile in 2006, where Alisma plantago aquatica hads already evolved resistance to sulfonylurea herbicides (SU). Several field trials with water seeded rice were conducted during 2003 and 2004 in Chile to determine efficacy, timing of application, spectrum of control, and control of SU-resistant A. plantago aquatic(a with the herbicide penoxsulam, either in single applications or in sequence with other herbicides. Penoxsulam was applied a) 12 days after seeding (DAS) into the water (I W), b) in postemergence after draining the water from field (ADW) at 35 DAS ore) IW followed by ADW applications of MCPA, cyhalofop, bentazon, or triclopyr. Penoxsulam was tested at 20, 30, and 40 g a.i. ha(-1). Comparisons were made with recommended rates of other IW treatments (metsulfuron, bensulfuron and cyclosulfomuron) and sequential applications of molinate (IW) followed by ADW applications of MCPA, cyhalofop, bentazon, or triclopyr. One IW penoxsulam application was sufficient to achieve broad-spectrum control: Echinochloa spp. (100% control), A.plantago-aquatica (80 to 100%), Schoenoplectus mucronatus (50 to 80%), and Cyperus difformis (80 to 100%). Rice yields in penoxsulam-treated plots were 30 to 56% higher than in the untreated controls. Yields with penoxsulam IW (all rates) were similar (P > 0.05) to those obtained using molinate (IW) followed by ADW applications of bentazon or MCPA. Although penoxsulam is an ALS inhibitor, it controlled A. plantago-aquatica resistant to metsulfuron and bensulfuron.