Pesticide trends in a tailwater recovery system in the Mississippi Delta

Authors: Nelson, Amanda; Moore, Matthew; Witthaus, Lindsey

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2022
Publication Date: 11/26/2022
Citation: Nelson, A.M., Moore, M.T., Witthaus, L.M. 2022. Pesticide trends in a tailwater recovery system in the Mississippi Delta. Agrosystems, Geosciences & Environment. 2(4):e20325. https://doi.org/10.1002/agg2.20325.
DOI: https://doi.org/10.1002/agg2.20325

Interpretive Summary: Tailwater recovery (TWR) systems are an important best management practice (BMP) used to address both water quality and quantity issues in the Mississippi Delta region. TWRs are systems for capturing surface water runoff to be later used for irrigation. TWRs consist of a ditch to capture runoff; an on-farm storage (OFS) reservoir to store captured water; and pumps to move surface water from the ditch into the OFS reservoir and to irrigate nearby fields. To determine if TWR systems are an effective way to reduce downstream pesticide loads, water quality and quantity data from a ditch and pond TWR system in Sunflower County, MS, were measured for five years. The objective of this study was to assess seasonal pesticide water quality trends. Twelve of the eighteen measured pesticides and metabolites were found in samples every season, from both the ditch and the reservoir. Several pesticides that have not been used in the United States in decades were detected, including DDT and its metabolites and five others. This demonstrates the environmental persistence of these prohibited pesticides. The reservoir contained higher pesticide levels for more of the pesticide varieties, which demonstrates a possible risk of cross-crop injury from recycling the water from the reservoir for irrigation purposes.

Technical Abstract: Tailwater recovery (TWR) systems are an important best management practice (BMP) used to address both water quality and quantity issues in the Mississippi Delta region. TWRs are surface water capture-and-irrigation reuse systems using a combination of ditches to capture surface water; an on-farm storage (OFS) reservoir to store captured surface water; and pumps to move surface water from ditches to the reservoir and from the reservoir to irrigate nearby fields. It is anticipated that TWR systems improve water quality by allowing agricultural contaminants to settle out in ditches and reservoirs, rather than being transported during irrigation to nearby fields and downstream aquatic systems. To determine if TWR systems are an effective way to reduce downstream pesticide transport, water samples from a ditch and reservoir TWR system in Sunflower County, MS, were routinely collected and analyzed for five years. Objectives of this study were to assess seasonal pesticide concentrations throughout the different components of the TWR system and identify any trends that may exist. Atrazine-desethyl, atrazine-desisopropyl, atrazine, clomazone, propanil, fipronil desulfinyl, metolachlor, fipronil, p,p'-DDT, bifenthrin, beta-cyfluthrin, and zeta-cypermethrin were found in every season, in both ditch and reservoir samples. Several pesticides that have not been used in the United States for decades were detected, including DDT and its metabolites, chlorpyrifos, dieldrin, heptachlor, lindane, methyl parathion, demonstrating their environmental persistence. The reservoir featured more types and higher concentrations of pesticides, indicating a possible risk of cross-crop injury from the recycling of the water from the reservoir for irrigation.