No Persistent Changes in Pasture Vegetation or Seed Bank Composition after Fallowing

Abstract

The practice of fallowing pastures during the growing season is intended to increase plant diversity and allow natural reseeding of forage grasses. Fallowing delivers these benefits in New Zealand, but has been adopted on rotationally stocked farms in the northeastern United States with little or no quantitative assessment. Allowing the pasture to remain ungrazed may allow weedy species to produce seeds, and could reduce legume populations. We measured the seed bank composition (n = 23) and aboveground vegetation (n = 32) in paddocks that had been fallowed from 0–6 yr previously on an organic dairy in Maryland. Transect sampling was used to characterize the canopy cover of the dominant species three times per year for 3 yr. Germinable seed was identified from 5‐cm soil cores collected in the spring and autumn in 2 yr. Fallowing did not produce any changes that persisted for more than 2 yr in either the seed bank or the vegetation of this farm. Tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] and other pasture grasses set seed, increasing in the seed bank during the fallow year, but this did not produce long‐term changes in either the seed bank or the vegetation. The proportion of weedy forbs in the seed bank increased, and the legume cover decreased, but only temporarily. Natural reseeding of tall fescue promoted by fallowing did not cause changes in the vegetation, but could lead to increased endophyte infestation in the endophyte‐free tall fescue originally planted.

Nitrogen Input Effects on Herbage Accumulation and Presence of Pasture Plant Species

“…Changing amount and form of N input in these management strategies had no affect on presence of perennial pasture species. While Kentucky bluegrass is a perennial grass commonly found in temperature pasture studies (Guretzky et al, 2005; Goslee et al, 2009), we did not find evidence that Kentucky bluegrass would increase with reduction of N input in CONT or a change of N amount and form in SUPP. Frequency of occurrence of Kentucky bluegrass was similar among treatments and years, averaging 11.7%.…”

“…Annuals such as foxtail are well adapted to pastures, but their seed often lie dormant in the seed bank until favorable disturbances and environmental conditions promote germination and emergence (Dekker, 2003). Their emergence in pastures may be difficult to predict as composition of aboveground vegetation bears little resemblance to composition of soil seed banks where annual grasses and forbs dominate (Tracy and Sanderson, 2000; Sanderson et al, 2007; Goslee et al, 2009). Recent experiments have focused on the role of forage plant species richness and diversity as a means of resisting annual and perennial weeds, including forbs and grasses, in pastures.…”

Soil seed bank community structure of pastures and hayfields on an organic farm

“…Most seeds in grassland soils occur in the top 5 cm (Csontos 2007), hence the 5-cm sampling depth in our study. The sample depth and number of samples per point and field is consistent with our previous research (Tracy and Sanderson 2000a;Sanderson et al 2007;Goslee et al 2009). The pairs of soil cores were crushed and mixed in the field and combined for each georeferenced point within a plot resulting in 27 individual samples of two soil cores each.…”

“…In pasture soils of the northeastern USA, seed banks generally are dominated by annual and perennial forbs (Tracy and Sanderson 2000a;Sanderson et al 2007;Goslee et al 2009), many of which can become serious invasive weeds. Seed banks, however, can also contain seed of useful forage species, such as white and red clover (Trifolium repens L.; Trifolium pratense L.) and bluegrass (Poa pratensis L.).…”

Performance of sown species and weed ingress in new dairy pastures based on tall fescue and perennial ryegrass

“…For example, Virgona & Bowcher (2000) used basal cover to assess the persistence of tall fescue and three other perennial grass species over a 2-year period. Assessments of canopy cover have also been used to monitor changes in pasture vegetation and ingress of weeds (Setterfield et al 2005;Goslee et al 2009).…”