Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 1998
Publication Date: N/A
Interpretive Summary: Estimating the weed seed content of the soil is required for many vegetation monitoring projects including effects of weed management systems, decision aid models, and seasonal seedbank population dynamics. This estimation is usually accomplished by direct germination of the seed from a soil sample or physical extraction of the seeds combined with a viability assessment. The procedures used to separate seed material from soil alter the seed environment for some period. This change in environment has the potential to affect seed behavior. Our objective was to more fully evaluate the effect of a commonly used centrifugation/floatation seed extraction procedure on the germination of giant foxtail seed. We found that the extraction procedure reduced seed germination by up to 40% compared with untreated seeds. These results suggest that the centrifugation/floatation seed extraction method should not be used for extracting giant foxtail seeds from soil if detailed information on germination is needed. A more gentle extraction procedure is needed to preserve the germinability of the seed during and following extraction. These results are valuable to scientists conducting research on weed seed behavior in the soil. Improved methods of weed seed detection will ultimately improve our understanding of the behavior of weeds and help provide farmers and other land managers better tools to manage weeds.
Changes in seedbank seed density are often monitored by removing seeds from soil samples. One extraction method accomplishes this by creating a slurry of soil and a concentrated inorganic salt solution. Centrifugation is then used to separate materials of differing densities. We have found that centrifugation of giant foxtail seeds in 3.2 M potassium carbonate solution as conducted in a centrifugation/floatation extraction method can reduce viability as measured by germination and tetrazolium tests. In one experiment, centrifugation/floatation separation reduced germination of giant foxtail seeds from 94 to 52%. The likely cause of seed damage was the high pH of the potassium carbonate solution in conjunction with the increased hydrostatic pressure due to centrifugation. This centrifugation effect, however, did not alter the viability estimates if a pressure test was used to assess seed viability.