Role of Nitrogen in Herbage Production by Agrostis-Festuca Hill Grassland

Abstract

The role of nitrogen (N) in limiting herbage production was assessed in an altitudinal sequence of Agrostis-Festuca grasslands in the Moor House National Nature Reserve. For most of the growing season the concentration of ammonium-N found in the soils at the times of sampling greatly exceeded that of nitrate-N. Laboratory determinations of soil N mineralization rates at field growing season temperatures showed that mineral N accumulated almost entirely as nitrate in samples from lower altitudes and as ammonium in soil samples taken at the highest altitude. A linear relationship between the mean annual concentration of N in the herbage and primary production in the four grassland sites suggests that soil N supply was a limiting factor (...)