Assessing nitrogen and phosphorus efficiency at farm and catchment scale using nutrient budgets

Farm nutrient budgets related to 1994 were calculated for seven farm types, accounting for similar to 90% of the agricultural land in the River Y han catchment, NE Scotland. The magnitude offIuxes of nitrogen (N) and phosphorus (P) at the catchment scale in relation to these farm types was also assessed. Positive budgets were calculated for all farm types, with the largest surpluses estimated for intensive Livestock units. Nutrient efficiency, defined as a percentage of outgoing over incoming nutrients, ranged from 11% (N) and 21% (P) on 'cattle and sheep' farms in less favoured areas to 54% (both N and P) on 'cereal' farms. The contribution from cropping versus Livestock farming in the total efficiency varied widely between farm types. At the catchment scale the surplus associated with grassland and Livestock (225 and 37kg ha(-1) of N and P) clearly exceeded that associated with arable crops (44 and 19kg ha(-1) of N and P). (C) 2000 Society of Chemical Industry.