Milliken, Caitlin, Biology, Susquehanna University, 514 University Ave, Selinsgrove, PA, 17870, Doucette@susqu.edu; Persons, Matthew, Biology Susquehanna University 514 University Ave Selinsgrove PA, 17870, email@example.com.
The earthworm, Lumbricus terrestris, frequently buries seeds (drawdown) and may predate upon the seed or the radicle as it germinates; however, it is unknown whether herbicides can affect worm seed preference and drawdown behavior or how these interact with germination probabilities. We tested the effect of four herbicide treatments: glufosinate (Surmise Pro®), glyphosate (Hi-Yield Killzall®), both, or neither (control) on mortality, weight gain, and drawdown behavior as well as the effect of herbicide and the presence or absence of a worm on the germination of barley (Hordeum vulgare) and einkorn (Triticum monooccum) (n=25-26 subjects per treatment; N=255). Each earthworm was given a simultaneous choice between four water-treated seeds (control) and four herbicide-treated seeds (on the herbicide-sprayed half of the container) or eight water-treated seeds in the double control. Germination, the number of radicles or shoots present, was recorded according to treatment side (herbicide-treated or control). In treatment containers with no worm present, only germination was recorded. Drawdown and germination were recorded every four days over a 36-day period, and seeds were removed from the soil surface and new seeds were deposited after every observation period. We found no significant difference in worm mortality across herbicide treatments but found significant treatment side effects for total seeds buried by the end of the experiment. Worms drew down significantly more barley than einkorn, and significantly more seeds were drawn down from the control side of the container than the herbicide-treated side. Fewest seeds were drawn down when seeds were sprayed with both glufosinate and glyphosate. We found significantly reduced weight gain in all herbicide treatments compared to the control. Herbicide application can affect the seed choice of earthworms that aid in bioturbation and burial of seeds, effectively altering the impact of worms on agriculture.
Herbicide, anecic, diet, germination