Retrieval and identification of weed seeds from landscape soils
2005
Mogensen, S.H.A.C. | Allen, P.S. | Jeffery, L.S.
A method for recovering seeds in soils was developed in collaboration with the United States Department of Transportation. Two approaches were considered: 1) separating seeds via wet-sieving and 2) seedling grow-out tests. Three types of samples were included: field topsoil, commercial topsoil and municipal compost. The wet-sieving procedure used sodium hexametaphosphate to disperse soil samples. Samples were washed through a set of three sieves with decreasing mesh diameters. Seeds collected from each of the sieves were sorted by hand, identified and counted by species. For the seedling grow-out tests, soils collected from sieves and the catchment bucket, as well as unsieved soil samples, were saturated with a solution containing gibberellic acid and potassium nitrate, then kept moistened under greenhouse conditions for 28 d. Seeds of 23 weed species were found in the commercial topsoils using the wet-sieving technique, seven of which are on the Utah noxious weed list. A higher percentage of the seeds present were retrieved from smaller samples (40 cm3). Seedling grow-out tests were laborious and failed to detect as many seeds and species as the wet-sieving procedure. Results of this study suggest that screening procedures can effectively identify and quantify weed seeds in soils, but confirm that seedling grow-out tests are impractical. As experts in seed identification, seed analysts may be the ideal group to conduct soil tests on weed seeds.
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