Long-term effects of fertilizer on soil nutrient concentration, yield, forage quality and floristic composition of a hay meadow in the Eifel mountains, Germany

A long-term fertilizer experiment, which was set up in 1941 on extensively grazed heathland, naturally dominated by Calluna vulgaris L. and Nardus stricta L., is presented. The turf layer was grubbed and reseeded with a grass/legume mixture, and plots were fertilized with (a) lime only as calcium (including magnesium), (2) lime and nitrogen (Ca/N), (3) lime, nitrogen and phosphorus (Ca/N/P₂O₅) and (4) lime, nitrogen, phosphorus and potassium (Ca/N/P₂O₅/KCl and Ca/N/P₂O₅/K₂SO₄). Since 1941 these experimental plots have been mown but not grazed.
After 50 years of imposing the experimental treatments, dry-matter (DM) yield was found to be positively affected by N, P and K application. Soil N and P concentrations were significantly higher in fertilized than in unfertilized plots. No differences in soil K concentration were found between the two treatments with KCl and K₂SO₄. Net energy concentration in the plant DM was highest with the Ca/N treatment, but differences were slight. Crude protein concentrations varied from about 110 to 170 g kg^–1 DM. In all plots and all years protein concentrations were lower in the first cuts than in the second cuts.
Considerable differences in floristic composition were found between different fertilizer treatments. The treatments receiving only Ca contained more than sixty species, many of them representative of oligotrophic extensively managed grassland. In fully fertilized plots, herbs were suppressed by tall-growing grasses. In these plots the number of species was low.