ARS | Publication request: The effect of pasture fallowing on plant community cover and seed bank properties

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 21, 2009
Publication Date: N/A

Interpretive Summary: Some grazers in the northeastern United States have adopted fallowing, the practice of leaving pastures ungrazed for a period to encourage reseeding and rejuvenation, although fallowing has not been tested for efficacy in this region. The lack of mowing or grazing may increase grass seed production, but also decrease legume populations and increase weed abundances. On a farm in Maryland that had pastures fallowed from 0-6 years ago, only temporary changes in the seed bank and the above-ground vegetation were observed. More grass and weed seeds were produced, but they did not persist in the seed bank or lead to longer-term differences in pasture composition. Fallowing does not appear to be a viable strategy for pasture regeneration in the northeastern United States.

Technical Abstract: The practice of fallowing pastures in a rotational grazing dairy system is believed to increase plant diversity, increase organic matter and improve the soil. Fallowing is practiced in New Zealand, and delivers these benefits, but has been adopted in the northeastern United States with little quantitative assessment. Growing-season fallowing did not produce any changes that persisted for more than two years in either the seed bank or the vegetation of the Maryland farm studied, with paddocks fallowed from 0-6 yr prior to sampling. Tall fescue and other pasture grasses did produce a short-term increase in the seed bank, but this did not lead to long-term seed bank changes or alterations in the vegetation composition. The hypothesized negative effects ¿ increased weed abundance and decreased legume populations ¿ were also not seen. The proportion of weedy forbs in the seed bank increased, but only temporarily. Although natural reseeding of tall fescue promoted by pastoral fallowing did not produce quantifiable changes in the vegetation, it could be promoting the increase of wild-type endophyte in the endophyte-free tall fescue originally planted. Fallowing does not appear to be a viable strategy for pasture regeneration in the northeastern United States.