Nutrient deficiency in undisturbed, drained and rewetted peat soils tested with Holcus lanatus

SUMMARY Two fen peat soils, supporting a species‐rich fen vegetation with a high nature value, and two accompanying drained fen peat soils, supporting vegetation types with a low nature value, were subjected to a study on nutrient deficiency. This study tested what effect rewetting of drained fen peat soils had on the nutrient deficiency. In each of the study areas, soil was collected from the wet site and from a neighbouring drained site. Holcus lanatus was used as a phytometer screening the wet soil under wet conditions and the drained soil when drained or rewetted. The soil taken from the wet site revealed a higher yield than the soil from the drained site in both study areas. Additional supply of K, in combination with N or P supply, further increased the biomass yield. K‐deficiency was even stronger in the drained site of both study areas. Experimental rewetting did not entirely remove this deficiency and additionally enhanced N‐deficiency. The results from this phytometer approach are discussed as related to results from field and laboratory experiments with vegetation as object of research.