Submitted to: Extension Fact Sheets
Publication Type: Other
Publication Acceptance Date: March 2, 2009
Publication Date: March 3, 2009
Citation: Sanderson, M.A. 2009. Pasture seed banks. Northeast Pasture Consortium Fact Sheets. p. 1.
In our surveys of northeastern pastures, we found the equivalent of more than 8 million seeds per acre in the surface soil (the top four inches) from the seed bank study. These seeds came from 58 species of plants. The annual forbs (all broadleaf plants with the exception of legumes and trees) dominated the seed bank with more than 4 million seeds per acre in the top four inches of soil. This class of plants included mainly weeds such as yellow rocket, lambsquarter, mustard, and shepherd’s purse. Dandelion and broadleaf plantain contributed most of the 1.2 million seeds per acre of perennial forbs in the seed bank. Green and yellow foxtail along with annual bluegrass and barnyard grass dominated the 1 million seeds per acre we found of the annual grasses. Kentucky bluegrass was the most abundant perennial grass seed found in pasture soils, equivalent to about l lb of seed per acre. White clover contributed to about 1 to 2 lbs of seed per acre in the legume component of the seed bank. Thus, in the northeastern U.S., bluegrass and white clover will supply most of the forages in the seed bank that may contribute to maintaining a pasture stand. Interestingly, even though most of the seeds in the soil seed bank were annual forbs, the plants growing above ground were nearly all bluegrass and white clover. There was only a 44% correspondence between the plant species found in seeds below ground and the plants found growing aboveground. Thus, you cannot exactly know what is in the soil seed bank by looking at what is growing in the pasture. The large number of weedy seeds in the pasture seed bank means that any gaps or bare spots in the sod will likely be filled by a weed from the seed bank. If not controlled, these weeds can contribute more seeds to the seed bank in a vicious cycle of weed invasion. Thus, maintaining a dense, vigorous pasture is critical.