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Table 1 Terms used in estimation of the gross nitrogen surplus

From: Environmental Efficiency and Pollution Costs of Nitrogen Surplus in Dairy Farms: A Parametric Hyperbolic Technology Distance Function Approach

Terms Method of estimation Sources of information
Inputs   
a. Mineral fertilizer Quantity of mineral fertiliser (kg) × nutrient content Teagasc National Farm Survey (NFS, Republic of Ireland) Farm Business Survey (FBS), Northern Ireland
b. Organic fertilisers (excluding livestock manure) Quantity of organic fertilizer (kg) × nutrient content The use of organic fertilizer in the study area is negligible and therefore was not included in the calculations
c. Livestock manure Annual average population of animals (heads) × manure excretion coefficients (kg nutrient/head year) Teagasc National Farm Survey (NFS), Farm Business Survey (FBS). DAERA (2017), Yan et al. (2006), Dairyman (2011)
d. Other inputs (seeds) kg nutrient per ha harvested area × utilised agricultural area (ha) OECD and Eurostat nutrient budgets methodology and handbook, Teagasc National Farm Survey (NFS, Republic of Ireland) and Farm Business Survey, Northern Ireland; contribution is negligible
e. Atmospheric nutrient deposition Utilised agricultural area (UAA) [ha] × nutrient deposition rate (kg/ha) Estimated based on data from literature (Eurostat 2013; The European Monitoring and Evaluation Programme (EMEP) 2014 data)
f. Biological nutrient fixation Utilised agricultural area (UAA) [ha] × nutrient fixation rate (kg/ha) A fixed amount was assumed based on literature
g. Total inputs a + b + c + d + e + f  
Outputs
h. Crop production Crop output (kg of dry-matter) × nutrient content (kg/kg of dry-matter) Teagasc National Farm Survey (NFS, Republic of Ireland), Farm Business Survey, Northern Ireland, Ewing (2002), and McDonald et al. (2002)
i. harvested and grazed grass Quantity of pasture consumed on-farm through grazing and silage × nutrient content of grass (in kg/kg of dry-matter) Teagasc National Farm Survey (NFS, Republic of Ireland), NRC (2001), Farm Business Survey, Northern Ireland
j. Crop residues removed Crop residues removed × nutrient content (kg/kg of dry-matter) Contribution is negligible and therefore was not included in the calculations
k. Total outputs h + i + j  
Gross Nutrient Balance (GNB) g–k