The reclamation of bracken-dominated pastures in Bulgaria using asulam andfertilizers

Bracken (Pteridium aquilinum) is a major weed of considerable economic conc ern in upland pastures in Bulgaria and elsewhere in Europe. Between 1993 an d 1998, a field experiment was carried out to rest methods for restoring pr oductive meadows. Initially, spraying asulam (4.8 kg a.i. ha(-1)) was used ro control the bracken on the sire; this was achieved in terms of reduced f rond densities and a higher level of grassland establishment. This grasslan d was dominated by Vicia cassubica and the perennial grasses Agrostis vulga ris, Dactylis glomerata, Festuca rubra. Holcus lanatus and Poa pratensis. After 2 years, a fertilizer addition experiment was started with four treat ments (no fertilizer; addition of phosphorus: addition of nitrogen and phos phorus: addition of nitrogen, phosphorus and potassium. The phosphorus and potassium fertilizers were applied annually in the early spring at 80 kg of P ha(-1) year(-1) and 50 kg of K ha(-1) year(-1), and nitrogen was added a t the start of grass growth at 60 kg of N ha(-1) year(-1). Ar the same time , a twice-yearly hay-cutting regime was implemented. Fertilizer addition in creased both the quantity and the quality of the resulting grassland. The h erbage dry matter was increased by at least a factor of two depending on fe rtilizer combination, and there was an increase in grass and legume cover a nd a decrease in both weed cover and bracken recovery. However, although br acken recovery was inversely related to grassland production, there was a c onsistent increase in bracken density across all treatments between 1997 an d 1998, suggesting that increasing herbage biomass merely delays bracken re covery. The implications of these findings are discussed.