The productivity and response to inorganic fertilisers of species-rich wetland hay meadows on the Somerset moors: the effect of nitrogen, phosphorus and potassium on herbage production

The effects of fertilizer nitrogen (N), phosphorus (P) and potassium (K) on herbage production were investigated in herb-rich hay meadows in Somerset, UK. Swards were cut after 1 July each year, followed by one or two aftermath cuts. Dry-matter (DM) yield at cutting, metabolizable energy (ME) production and recovery of N, P and K were measured over 4 years. Total annual DM production increased from 4.7 t ha-1 without fertilizers to 10.5 t ha-1 with 200 kg N, 75 kg P and 200 kg K ha-1 per year, and ME output from 38.8 GJ ha-1 to 92.5 GJ ha-1. Applying moderate replacement rates of P and K without N increased annual DM and N yields by 43% and 36% respectively, but N response was modest unless high rates of P and K were used. Annual ME output and recovery of N, P and K were all significantly increased by taking an additional, earlier cut for silage, even though DM yield was unaffected. The results suggest that potential output of these meadows is similar to that of a wide range of less diverse permanent pastures. Data from this and a concurrent experiment will help to estimate the financial implications of fertilizer and cutting date restrictions within Sites of Special Scientific Interest and the wider Environmentally Sensitive Areas

The productivity and response to inorganic fertilizers of species- rich wetland hay meadows on the Somerset Moors: nitrogen response under hay cutting and aftermath grazing

The productivity and response to fertilizer nitrogen (N) was measured in herb-rich wetland hay meadows within a Site of Special Scientific Interest (SSSI) in Somerset, UK. Output from hay cut after 1 July each year and from beef production at aftermath grazing was measured over a total of 4 years. Total utilized metabolizable energy (UME) output averaged from 40.6 GJ ha-1 year-1 without fertilizers to 61.7 GJ ha-1 at 200 kg N ha-1 (N-200), the highest rate used, with about two-thirds of this output from hay. N response was markedly curvilinear above about 50 kg N ha-1, but data from a concurrent experiment suggested that the comparatively low replacement rates of P and K applied were limiting at higher N rates. When hay cutting was delayed until early August in a wet year, yield response to N was lost because fertilized swards had passed a peak in yield several weeks before harvest. Compared with other published data, the results suggest that output and response to N is not constrained by the diversity of the flora or the damp conditions. The data will help to estimate the financial implications for farmers of restricted or zero fertilizer use within SSSIs and the wider Environmentally Sensitive Areas