Reducing pesticide transport in surface and subsurface irrigation return flow in specialty crop production

Authors: ABDI, DAMON - Michigan State University; Owen Jr, James - Jim; WILSON, P. CHRISTOPHER - University Of Florida; HINZ, FRANCISCA - University Of Florida; CREGG, BERT - Michigan State University; FERNANDEZ, R. TOM - Michigan State University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2021
Publication Date: 8/20/2021
Publication URL: https://handle.nal.usda.gov/10113/7482971
Citation: Abdi, D., Owen Jr, J.S., Wilson, P., Hinz, F., Cregg, B., Fernandez, R. 2021. Reducing pesticide transport in surface and subsurface irrigation return flow in specialty crop production. Agricultural Water Management. 256. Article 107124. https://doi.org/10.1016/j.agwat.2021.107124.
DOI: https://doi.org/10.1016/j.agwat.2021.107124

Interpretive Summary: Pesticides are critical to maintaining pest-free, aesthetically appealing crops, with herbicides, insecticides, and fungicides typically applied multiple times per year. Off-site transport of potentially harmful agrichemicals via runoff or reintroduction in recycled water is of increasing concern for water security. Within the ornamental crop industry, over 350 modes of action, spanning several pesticide and chemical classes, were used in 2009. This study investigated movement of nine pesticides, varying in physiochemical properties and mobility classes, and partitioning between irrigation surface and subsurface irrigation return flow when using either overhead systems or micro-irrigation systems applying water based on growing media moisture compared to a typical conventional irrigation practice within a model nursery. Irrigating based on the growing media moisture reduced the volume of water applied and subsequent return flow. Reductions in the volume of water applied via overhead irrigation reduced the amount of water applied to non-target areas reducing return flow. No differences were identified in subsurface irrigation return flow volumes between the treatments and the control; however, the consistently greater volumes of surface irrigation return flow from the control indicates that more efficient irrigation practices have a greater impact on surface return volume than subsurface irrigation return flow volume. Pesticide mobility in surface and subsurface irrigation return flow was reflective of each compound’s physiochemical properties, with more soluble pesticides capable of moving in both surface and subsurface irrigation return flow, while less soluble pesticides were typically only mobile in surface irrigation return flow. For all pesticides studied, surface irrigation return flow typically exported a greater amount of each pesticide. Practical strategies to minimize pesticide movement is selecting pesticides possessing low solubilities/high adsorption coefficients, when possible. Regardless of pesticide physiochemical properties, implementing irrigation practices that delay irrigation applications, reduce irrigation volume, and/or provide water directly to crops/containers are management practices that effectively limit pesticide movement, particularly highly mobile compounds.

Technical Abstract: This study investigated the transport of 9 pesticides in surface and subsurface irrigation return flow from a container plant production system over 3 16-day monitoring periods. Pesticides were applied 3 times during the year and the pesticides were selected to provide a range of physiochemical properties. Pesticides are most commonly transported in water and irrigation return flow is a driving factor, therefore, irrigation methods were investigated to determine effects on irrigation return flow volume and transport of pesticides. A control overhead irrigation and two treatments irrigating based on substrate volumetric moisture content (') were used. Pesticide transport in irrigation return flow was related to days after application, physiochemical properties and irrigation method. Additionally, pesticide transport was disproportionately reduced in respect to physiochemical properties, in subsurface irrigation return flow in response to irrigation methods. '-based irrigation treatments reduced irrigation volume applied by 49% and 77% compared to the control leading to a reduction in the volume of surface irrigation return flow by 71% and 92%. The '-based treatments reduced the total combined volume of irrigation return flow by 52% and 78% versus the control. In most cases, pesticides movement in surface irrigation return flow exhibited a linear or quadratic decrease for the control, while pesticide movement via subsurface irrigation return flow was related more to physiochemical properties limiting mobility rather than irrigation return flow volume or irrigation practice. This study demonstrates pesticide movement in irrigation return flow can be substantially reduced by selecting pesticides with low solubility/high adsorption coefficients whenever possible, and reducing the volume/application of irrigation to non-target areas.