Vegetated ditches as a management practice in irrigated alfalfa

Abstract

The organophosphate (OP) insecticides diazinon and chlorpyrifos have been frequently detected in the San Joaquin River, California, USA. Irrigation tail waters are a significant source of OP pesticides in the watershed. This study tested several management practices for reducing offsite movement of chlorpyrifos to surface water from flood irrigated alfalfa. Management practices evaluated include (1) a constructed, vegetated irrigation tailwater return ditch and (2) increased lag time between chlorpyrifos application and start of flood irrigation. Chlorpyrifos concentrations in whole-water samples of irrigation runoff were variable and ranged from 0.22 microg/l to a maximum of 1.67 microg/l. The median concentration reduction at the end of a 200 m vegetated ditch was 38% compared to 1% in an adjacent conventional tail water ditch. Runoff data collected represented first flush runoff from sets that were irrigated between 48 and 144 h after chlorpyrifos application. There was no consistent effect of irrigation lag time on chlorpyrifos concentration in tailwater for lag times of up to 144 h. Consequently these data indicate that delayed irrigation is not an effective management practice for reducing chlorpyrifos off-site movement to surface water in California flood irrigated alfalfa.

Managing ditches for agroecological engineering of landscape. A review

“…Kröger et al (2009) estimated a chemical retention time that was three times higher for a vegetated ditch than for a geomorphologically similar, non-vegetated ditch. Vegetation and ditch sediments provide efficient retention sites for nutrients (Needelman et al 2007;Smith and Pappas 2007) and pesticides (Gill et al 2008;Margoum et al 2003;Margoum et al 2001;Pappas and Smith 2007). The removal of these sediments is therefore likely to reduce the retention capacity of the ditches.…”

“…Both of these papers mentioned the impact of ditches on pesticide fate but, due to a lack of studies, did not highlight the complexity of this impact due to numerous molecules exhibiting a large range of chemical properties and, in turn, behaviors. From 2008, however, several case studies explored the retention ability of vegetated ditches depending on the pesticide chemical properties (Elsaesser et al 2013;Gill et al 2008;Moore et al 2011;Passeport et al 2011a), now enabling a more comprehensive review on pesticide fate in ditches. In their reviews, Herzon and Helenius (2008) and Needelman et al (2007) indicated that drainage ditches can be managed for multiple functions, providing examples of management practices with positive effects.…”

Exposures of Aquatic Organisms to the Organophosphorus Insecticide, Chlorpyrifos Resulting from Use in the United States

“…1); second, the historical detections of CPY reported from monitoring studies conducted in the state (CDPR 2012a; CEPA 2011a, b; USGS 2013); third, the availability of detailed records on pesticide applications from the California Department of Pesticide Regulation's (CDPR) Pesticide Use Reporting (PUR) database (CDPR 2012b); and fourth, because of the intensive use of furrow and flood irrigation on crops registered for use with CPY in the state (Orang et al 2008). Losses in furrow and flood irrigation tail-water have been identified as a major cause of transport of pesticides, including CPY, to nontarget aquatic systems (Budd et al 2009;Gill et al 2008;Long et al 2010;Starner et al 2005). This pathway could not be simulated with the National Pesticide Assessment (NPAT) model.…”

Controlling Offsite Movement of Agricultural Chemical Residues: Winegrapes

“…Gill et al (2008) applied chlorpyrifos at 1 pint per acre and found a 40% reduction in the water column concentration after passage through a vegetated ditch, although the outflow water was still at 33 times the water quality standard of 15 parts per trillion. Anderson et al (2008) found an average 35% reduction of chlorpyrifos concentration in runoff water in two evaluations after passage through a vegetative ditch containing aquatic vegetation.…”

“…Anderson et al (2008) found nearly 100% reduction of permethrin after treatment in a vegetated ditch. Additionally, Gill et al (2008) found a 25% reduction of pyrethroid (lambda-cyhalothrin) residues after moving runoff water through a vegetated ditch.…”