Long-term dynamics of standing crop and species composition after the cessation of fertilizer application to mown grassland

Reduce chemical inputs in grassland management

A replicated trial from 1972 to 1988 in the Drentsche A nature reserve, Drenthe, the Netherlands (Olff & Bakker 1991) found that stopping fertilizer inputs on grassland mown annually for hay led to a gradual change in plant species composition, and an increase in the number of species in two out of three experimental fields. All three fields had a maximum number of plant species recorded in the middle of the study (between 1980 and 1985), followed by a slight decrease in the number of species as species initially present were replaced. In all fields, previously dominant grass species Yorkshire fog Holcus lanatus and creeping bent Agrostis stolonifera were replaced by creeping buttercup Ranunculus repens and sweet vernal grass Anthoxanthum odoratum, amongst others. In 1988 there were 23 and 28 species on two peaty fields, which had risen from 19 and 20 species in 1974, and 30 plant species on a sandy field, the same number as in 1974. Plant species were monitored in six 4 m² quadrats each June from 1974 to 1988, on two 50 x 10 m fields on peaty soil and one 20 x 10 m field on sandy soil. Fertilizer application stopped in 1972, and all fields were cut for hay either once or twice, but no earlier than July.