Persistence of sown species and ingress of unsown species in agriculturally improved hill swards

Abstract

Swards on wet hill land in mid-Wales, which had been converted from semi-natural rough grazing (dominated by Molinia caerulea, Nardus stricta or Calluna vulgaris) by surface-sowing in the period 1965–75, were examined in 1982, 1984 and 1996/97, using a point quadrat technique, in order to record the extent to which the sown species had persisted and the ingress of unsown species.

Lolium perenne had persisted to 1996/97 to the extent of being 20% of the sward on sites c. 300 m above sea level and 3% on sites at c. 500 m. Trifolium repens had persisted to c. 7% of the sward at both elevations. Festuca rubra was 6% of the sward on the higher sites and close to zero on the lower ones. The other main sown species, Phleum pratense, was present in only trace amounts on all sites in 1982, 1984 and 1996/97. The failure of T. repens to persist in larger amounts was attributed in part to below optimum soil pH and K and to the annual application of fertilizer N. The decline in L. perenne was attributed in part to severe winters on the higher sites and to below optimum soil K and pH. Agrostis spp. were the most prominent of the unsown species. Poa spp. appeared to stabilize at 8–15% of the sward. Stellaria media and Holcus lanatus became fairly prominent on the lower sites and Anthoxanthum odoratum on the higher sites. A supplementary study of the lower sites showed that the lime had been effective to at least the 20–25 cm layer of soil, that the distribution of plant roots in the soil was not abnormal, that T. repens plants had a satisfactory number of root nodules and that the soil contained a satisfactory number of earthworms.