Reversion of vegetation following the cessation of fertilizer application

Reduce chemical inputs in grassland management

A replicated, controlled, before-and-after trial from 1991 to 1993 on a species-rich hay meadow at Tadham Moor in Somerset, UK (Mountford et al. 1996) found that ceasing fertilizer application for three years led to a gradual increase in the number of plant species. All plots where fertilizer was stopped in 1991, having been applied at four different levels from 1986 to 1989, had fewer plant species than unfertilized control plots throughout the experiment (they did not revert to the original condition in three years). However, in 1992 and 1993, Yorkshire fog Holcus lanatus and perennial rye grass Lolium perenne declined in the plots without fertilizer, and were being replaced by common bent Agrostis capillaris and crested dog’s tail Cynosurus cristatus. In 1993, plots without fertilizer had more plant species than plots with continued fertilizer, and species richness was increasing at an estimated 1 species/m²/year in all treatments. The average estimated time for the vegetation to revert to the original community following three years of fertilizer application was between four (at 25 kg N/ha/year) and eight years (for 50-200 kg N/ha/year). From 1986-1989, experimental plots (1.5 x 5 m) were fertilized at five different levels: 0 (control plots), 25, 50, 100 and 200 kg N/ha/year. There were three replicates of each treatment. From 1990 to 1993, half of each plot continued with the same fertilizer treatment as before, the other half stopped receiving any fertilizer. Plants were monitored on sixteen 1 m² quadrats/plot, fifteen times between 1991 and 1993.