Emergence and Survival of Pasture Species Sown in Monocultures or Mixtures

Received for publication August 4, 2004. Plant–plant interactions during seedling establishment can markedly affect the composition of pasture communities. This research examined the emergence, mortality, and early growth of four forage species commonly found in temperate northeastern U.S. pastures. Species were selected based on functional group (grass vs. legume) and relative drought tolerance. Drought-tolerant species included ‘Penlate’ orchardgrass (Dactylis glomerata L.) and ‘Viking’ birdsfoot trefoil (Lotus corniculatus L.), while drought-sensitive species included ‘Basion’ perennial ryegrass (Lolium perenne L.) and ‘Will’ white clover (Trifolium repens L.). Seeds were sown as monocultures, as grass–legume binary mixtures, and as a complex, four-species mixture. Mixture complexity had only minor effects on seedling emergence. However, legume mortality was significantly reduced in the complex compared with other mixtures in a year when high temperature and drought stress limited seedling establishment. In most cases there was a negative effect of neighbors on survival as evidenced by reduced clustering of surviving compared with emerged seedlings and by a negative relationship between mortality rate and distance to the nearest neighbor. However, in a drought year, perennial ryegrass mortality decreased as distance to the nearest neighbor decreased, suggesting that survival was facilitated by the presence of neighbors. Although mixture complexity had significant effects on seedling emergence and mortality, species composition in the binary and complex mixtures could be predicted based on emergence and survival of monocultures. It appears that seedling emergence information gleaned from monocultures can be a useful tool for predicting initial species composition of more complex mixtures.