Pesticide mobility in surface and subsurface irrigation return flow in a container plant production system

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

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2025
Publication Date: 3/25/2025
Citation: Abdi, D., Owen Jr, J.S., Wilson, P.C., Hinz, F.O., Cregg, B.M., Fernandez, R.T. 2025. Pesticide mobility in surface and subsurface irrigation return flow in a container plant production system. Water. 17(7) Article #953. https://doi.org/10.3390/W17070953.
DOI: https://doi.org/10.3390/W17070953

Interpretive Summary: Chemical movement from agricultural sites are an environmental concern, with high input intensive agriculture elevating the risk of export. Containerized crop production necessitates continuous water, fertilizer, and pesticide inputs to ensure a salable product. Pesticides are critical to maintaining a pest free, aesthetically appealing ornamental crop; with pesticides typically applied multiple times per year. In this study, we investigated the quantity and concentration of ten pesticides in surface and subsurface irrigation return flow (IRF; i.e. runoff or leaching) within a model nursery when irrigated either by overhead or microirrigation. Mircoirrigation was applied daily in a set amount or based on feedback from sensors used for monitoring substrate moisture. The ten pesticides were selected not only for their common use in nursery production, but also for a wide spectrum of physiochemical properties, chiefly solubility and sorption coefficients. Surface IRF (i.e. runoff) was the predominant vector of movement for all pesticides, regardless of physiochemical properties, and pesticides were transported in the greatest quantities on days immediately following application. The benefits of irrigating using microirrigation systems extend beyond water conservation and can be used to limit IRF and the movement of pesticides. Reducing or eliminating surface irrigation return flow with microirrigation reduced the movement of all pesticides through this vector by over 90%. Retention of pesticides upon the nursery production surface may offer greater pest control and treatment efficacy, while also allowing preferable degradation mechanisms to occur. The use of microirrigation in container nursery production is an effective tool to reduce water use, reduce IRF and concomitant pesticide movement, and limit the economic and ecologic concerns of agrochemical transport.

Technical Abstract: This study investigates the movementof 10 pesticides in a container nursery production system using three irrigation methods. The research was conducted at an experimental nursery designed to collect surface and subsurface irrigation return flow. Irrigation was applied daily for overhead control and one microirrigation treatment, the second microirrigation treatment was scheduled based on substrate moisture sensors. Irrigation volume was reduced when using microirrigation by more than 75% and surface irrigation return flow by up to 100% compared to overhead irrigation. Subsurface irrigation return flow was reduced by 23-47% with microirrigation compared to the overhead irrigation. Pesticides were applied three times during the year using standard practices at label rates. In general, as pesticide solubility decreased and adsorption coefficients increased, there was less occurrence of the particular pesticide in surface and, to a greater extent, subsurface irrigation return flow. Pesticides with high solubility and low adsorption coefficients generally exhibited a high and nearly equal degree of mobility in the surface and subsurface irrigation return flow. Pesticides with high solubility were found in subsurface irrigation return flow across all the irrigation methods; whereas, moderately soluble/ moderately sorptive pesticides were found in greater quantities for treatments receiving greater volumes of irrigation. The pesticides with low solubility and high adsorption coefficients were not found in subsurface irrigation return flow. Reducing or eliminating surface irrigation return flow with microirrigation reduced the movement of all pesticides through this vector by over 90%. Reductions in pesticide movement via subsurface irrigation return flow were related more to physiochemical properties than water volume. This study demonstrates that pesticide movement in irrigation return flow can be reduced by selecting pesticides with low solubility and high adsorption coefficients whenever possible and by applying irrigation to only target areas with the minimal volume needed.