Gross nutrient balances: German experiences Volker Appel, BMELV-425 WORKING PARTY "AGRICULTURE AND ENVIRONMENT" OF THE STANDING COMMITTEE FOR AGRICULTURAL STATISTICS

WP Agriculture and environment, Dec, Introduction Nutrient use in agriculture  high importance for understanding interactions between agriculture and environment Plant production requires an adequate supply of nutrients in the soil ↨ Concerns about the environmental effects of nutrient surpluses (NO 3 - in ground water, emission of trace gases, P concentrations in surface waters)  Nitrogen balance = indicator in National Sustainability Strategy

WP Agriculture and environment, Dec, Calculation of regional nutrient balances The following results come from …. SCANUBA = Scale dependent nutrient balances German TAPAS 2007 action on calculating regional soil surface N balances (Julius Kühn-Institute / University of Gießen, 2008)

WP Agriculture and environment, Dec, Input and output variables of the national German N balance average NITROGEN INPUTS [%] Mineral fertilisers Organic fertilisers Livestock manure Atmospheric deposition Biological nitrogen fixation Seeds and planting material NITROGEN OUTPUTS [%] Cereals Oil crops Legumes Industrial crops Other crops Harvested fodder crops Pasture

WP Agriculture and environment, Dec, Assumptions 1.Nitrogen pool in the soil will remain unchanged. 2.Nitrogen losses by soil erosion / nitrogen enrichment due to sedimented material are unaccounted for. 3.Gaseous NO und N 2 emissions from nitrification and denitrification processes in soils are not included in the balance. 4.Non biotic nitrogen fixation from the atmosphere will not be considered.

WP Agriculture and environment, Dec, Data sources 1.land use data, yield/ha, livestock numbers: agricultural statistics 2.milk yield, regional share of different animal housing systems, volatilised NH 3 and N 2 O: National Inventory Report nitrogen input by deposition : „National implementation of the UNECE Convention on Long-range Transboundary Air Pollution“ N-coefficients: Ordinance on Fertilisation (Düngeverordnung) and publications by Association for Technology and Structures in Agriculture (KTBL)

WP Agriculture and environment, Dec, Computation procedure I Data on mineral fertilizer: reliable only at national level (and for large NUTS 1 regions)  1st step: calculation of Total N demand of crops at NUTS 3 = f (acreage, yield) 2nd step: Mineral N fertilisation = Total N demand of crops - livestock manure*deduction factor - organic fertilizer - legume N fixation (Assumption: farmers account for 100 % of N supplied, except livestock manure)

WP Agriculture and environment, Dec, Computation procedure II 3rd step: Compute deduction factor at national level, solving the last equation in reverse direction ↔ values between 0.15 and 0.4 (for different years) 4th step: Insert deduction factor into above equation to compute mineral fertilzer quantities at NUTS 3 level 5th step: Insert these data into the nitrogen balance

WP Agriculture and environment, Dec, Gross N balance 2003Net N balance 2003

WP Agriculture and environment, Dec, Problems within this approach Data gaps relevant at regional level: mineral fertiliser imports / exports of livestock manure organic secondary raw material yield of several field crops and permanent crops Assumption of optimal (100 %) use of mineral fertiliser  transfer of environmental problems to livestock manure. Uniform deduction factor for livestock manure!

WP Agriculture and environment, Dec, Possible ways forward Improve quality and remove uncertainties of single elements of the balance equation: site conditions ↔ N demand of crops check „top-down-approach“ with „bottom-up-approach“ using farm accountancy data → derive input/output coefficients and transfer functions (OSTERBURG/SCHMIDT/GAY, 2004; OSTERBURG/SCHMIDT, 2008) _______________________________________ Keep in mind: cost-benefit-ratio!

WP Agriculture and environment, Dec, N balance surplus for Germany sector balance, kg/ha UAA (3 year moving average) Source: Destatis, Sustainable Development in Germany - Indicator Report 2008 for the National Sustainability Strategy