Fertiliser nitrogen responses on two hill pastures of different phosphate fertiliser history

Fertiliser nitrogen responses with and without applied phosphate, were measured over spring on slopes and flat areas within two sheep‐grazed hill pastures of different P status. One pasture had received little phosphate in recent years and contained low levels of legume (9.2%) and ryegrass (6.3%), whereas the other had received large P inputs and contained substantially more legume (14.9%) and ryegrass (13.9%). Pasture N responses on both pastures were large in spite of differences in species composition. Application of phosphate along with the N fertiliser did not affect total pasture production, or grass species yields, on either pasture. Legume production was little affected by fertiliser N, but was substantially greater with P on lower P status soils. Increases in pasture production with N were similar on flat (0–10°) and steep (10–25°) sites, despite different productivity and species composition. This suggests that N deficiency over spring is general in these soils and essentially independent of pasture types.