Phytometric assessment of the fertility of undrained rich-fen soils.
To evaluate suitable methods for comparing soil fertility across a large number of undrained rich-fen sites the relationships between soil chemical conditions, phytometric assays and in situ crop yield in a representative range of samples from these ecosystems in England and Wales were examined. Correlation and regression analyses showed that only a few chemical variables were significantly related to variation in either in situ above-ground production or to phytometric response. Extracted and total concentrations of K and P showed a similar, weak, but significant relationship whilst N concentration had no relationship. Standard measurements of N, P and K concentrations in fen soils did not provide a reliable guide to their fertility. The phytometric response of Epilobium hirsutum seedlings was strongly related to in situ 'production' and may provide a better estimate of soil fertility. E. hirsutum is sensitive to high concentrations of available Fe and Mn, thus Phalaris arundinacea may be a better phytometer for soils rich in reduced toxins.