Effect of residual pesticides in recycled nursery runoff on growth and physiology of six ornamental shrubs

Authors: POUDYAL, SHITAL - Utah State University; ABDI, DAMON - Michigan State University; Owen Jr, James - Jim; FERNANDEZ, R. - Michigan State University; CREGG, BERT - Michigan State University

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2021
Publication Date: 12/21/2021
Citation: Poudyal, S., Abdi, D., Owen Jr, J.S., Fernandez, R.T., Cregg, B. 2021. Effect of residual pesticides in recycled nursery runoff on growth and physiology of six ornamental shrubs. Water, Air, and Soil Pollution. 233. Article 3. https://doi.org/10.1007/s11270-021-05468-7.
DOI: https://doi.org/10.1007/s11270-021-05468-7

Interpretive Summary: Nursery runoff may contain pesticide residues, which, if released off-site, could impair surrounding ecosystems. As one solution, nursery growers can retain runoff water on-site and recycle retained water to irrigate plants. However, concerns related to potential phytotoxicity caused by residual pesticides in recycled water discourage growers from recycling water. To evaluate phytotoxicity of plants irrigated with recycled water, we conducted a three-year field study simulating a commercial nursery growing practice. Irrigation treatments were applied to six ornamental taxa grown using raw, water recycled from a separate nursery bed containing treated with nine pesticides regularly, and recycled water treated by shale and woodchip bioreactors. Pesticide concentration recycled water was thousands of times lower compared to typical application rates and was dependent on pesticide solubility, pesticide adsorption and pesticide persistence. Neither plant physiology nor visual appearance was affected when receiving recycled water (runoff water with and without remediation). Results from this study further demonstrate the low-risks associated with using recycled water for irrigation of woody ornamental shrubs.

Technical Abstract: Nursery runoff may contain pesticide residues, which, if released off-site, could impair surrounding ecosystems. As a solution, nursery growers can retain runoff water on-site and recycle retained water to irrigate plants. However, concerns related to potential phytotoxicity caused by residual pesticides in recycled water discourage growers from recycling water. To evaluate plants irrigated with recycled water, we conducted a three-year field study simulating a commercial nursery growing practice. Irrigation treatments were applied to six ornamental taxa grown in a nursery production bed. Irrigation treatments were raw groundwater from the on-site well (control), water recycled from a separate nursery bed containing plants that were treated with nine pesticides regularly over the growing seasons, and recycled water from the nursery bed that had been remediated using heat-expanded shale aggregates and woodchip bioreactors. Plants receiving recycled water (runoff water with and without remediation) did not produce pesticide-related visual injury. However, result for growth index, chlorophyll SPAD index, dark-adapted fluorescence, and shoot biomass were irregular among raw groundwater and recycled water; for most instances, pesticides in recycled water did not reduce any of those parameters. Net photosynthesis and light-adapted fluorescence were similar for raw groundwater and recycled water. Results from this study demonstrate the possibility of using recycled water for irrigation of woody ornamental shrubs.