Comparison of methods to recover amaranth weed seeds from manure

One pathway by which Palmer amaranth (Amaranthus palmeri S. Watson) invades new areas is through importation of contaminated livestock feed, which then contaminates land-applied manure. If contaminated feed is suspected, detection tools are needed to test manure, but traditional methods are time consuming and often inconclusive. Although new genetic seed testing is making detection easier, methods to separate seed from contaminated manure are needed. Six methods were compared for their ability to recover 100 Palmer amaranth seeds added to bedded or nonbedded cattle manure: dry sieving, rinse sieving, manure saturation sieving without blending and with blending, and dispersion sieving without blending and with blending. Seed recovery was highest (>90%) with the rinse sieving method regardless of manure type. The dispersion methods are not recommended as they recovered <24.7% of seeds. Following each method, genetic testing successfully identified Palmer amaranth presence, indicating no interference of recovery method with DNA extraction.