The phosphorus cycle in northwest European agricultural soils Nutrihort September 17, 2013 Fien Amery Bart Vandecasteele Institute for Agricultural and Fisheries Research Plant Sciences Unit Agriculture and Fisheries Policy Area

Phosphorus in water and soil 2 Phosphorus (P): negative effects on water ecology (eutrophication) → Water Framework Directive → Nitrate Directive Target: agricultural P application Good, but… –Impact on soil and crops? –Efficient tool? –Differences among Member States? Literature study

Phosphorus in surface waters 3 Water Framework Directive Goal: good ecological status/potential of water bodies Each member state: –Define ecological reference condition and classifications for each surface water type –Relate ecology to chemical/physical conditions (P concentration) –P concentration standard for each surface water type

Phosphorus in surface waters 4 Water Framework Directive Intercalibration exercise between member states Guidance document (not legally binding) Rivers (Claussen et al., 2012) Flanders: 0.14 mg P/l mg ortho-P/l

Phosphorus in surface waters 5 Water Framework Directive Lakes (Claussen et al., 2012) Flanders: mg P/l

Phosphorus in surface waters 6 Difficult to compare: –Type of concentration –Statistics –Water type –Time of measurement –Monitoring network Groundwater (points/1000 km²) Surface water (points/1000 km²) Belgium 9938 Germany 31 Denmark 345 France 53 Ireland 13 The Netherlands 3313 United Kingdom 1333 Finland average Source: van Grinsven et al., 2012 Thresholds are exceeded in Europe: –60% of NiD measuring points in Flanders –57% of NiD measuring points in the Netherlands → P application in agriculture is targeted

Phosphorus in agricultural soils 7 Phosphorus losses from soil –In general: losses increase with increasing soil P concentration –Often: exponential increase above a threshold P concentration –Important: transport and hydrological factors → Keep soil P concentration under threshold Soil P concentration yield target zone P loss

Phosphorus in agricultural soils 8 BUT what about crop yields? –Farmers fear smaller crop yields –However: none/small yield reductions expected at P-input < P- export given the large soil P reserves in NW Europe Soil P concentration yield target zone P loss

Phosphorus in agricultural soils 9 Target zone: –optimum crop yields (agro-economical) –Minimal soil P losses (ecological) –Left of target zone: P input > P export –In target zone: P input = P export (equilibrium fertilisation) –Right of target zone: P input < P export Soil P concentration yield target zone P loss

How to reach the target zone? Sound fertilisation advice Target zone of fertilisation advice –often > economic/ecological target zone –Wide variation in Europe Soil P concentration yield target zone P loss Source: Jordan-Meille et al., 2012

How to reach the target zone? Sound fertilisation advice Flanders: highest target zone for fertilisation advice + fertilisation advice for target zone soils > P export Soil P concentration yield target zone P loss CropAdvise (kg P 2 O 5 /ha/yr) a P-export (kg P 2 O 5 /ha/yr) b Chicory8143 Broccoli13012 Celeriac11067 Leek11334 Salsify10327 Spinach13116 Brussels sprouts13233 Carrots13262 Strawberry14611 a Average for the target zone according to the Bodemkundige Dienst België (Maes, 2012) b Average in the Netherlands (Ehlert et al., 2009)

How to reach the target zone? Sound fertilisation advice A need for updated fertilisation advice –New knowledge and methods –Advice often based on trials from 40 years ago and limited tested crops Significant effort! Example: the Netherlands (see presentation 23) In addition: farmers often apply more than the recommended dose

How to reach the target zone? Application standards Phosphorus application standards to limit soil P concentrations –Most countries: no P limits a First numbers: for Numbers between brackets: proposed standards from 2017 on. Standard for phosphate saturated soils: 40 kg P 2 O 5 /ha/yr; b Agricultural system: grassland or arable crops; c Standards only for organic P fertilisation Country (region)DifferentiationP fertilisation standard (kg P 2 O 5 /ha/yr) Belgium (Flanders)Crop65-95 (55-90) a The NetherlandsSoil and agricultural system b IrelandSoil and crop0-286 Sweden-50 c Slovenia-120 c France (Brittany)Type of farm

How to reach the target zone? Application standards Differentiation of the P application standards? –Crop differentiation (Flanders, Belgium): P limit ≈ P-export –Soil P differentiation (the Netherlands): P limit according to P soil –Soil P and crop differentiation (Ireland) Soil P concentration yield target zone P loss Soil P concentration yield target zone P loss Soil P concentration yield target zone P loss Soil P concentration yield target zone P loss Soil P concentration yield target zone P loss Soil P concentration yield target zone P loss

How to reach the target zone? Application standards Flanders: no crop differentiation within the vegetable group: 65 kg P 2 O 5 /ha/yr = 28 kg P/ha/yr (2017: 55 kg P 2 O 5 /ha/yr = 24 kg P/ha/yr) Ireland: standards in kg P/ha/yr

How to reach the target zone? Application standards Flexibility in application standards? –The Netherlands: 20 kg P 2 O 5 /ha/yr transferrable to next year –The Netherlands and Flanders: P application by compost accounts for only 50% –Not present in legislation: higher application standards when more than one crop per year is grown

Remarks 17 Despite attemps to reduce P fertilisation, P concentrations in water bodies remain high –Low mobility of P –Legacy P –Contribution of point sources? –Even if P concentration decreases, ecology not ameliorated Alternatives –Targeting point sources –Targeting transport, edge-of-field measures (e.g. chemical soil amendments, capturing P in wetlands or filters, etc.)

Conclusion 18 Large differences in Europe –P concentration standards in water bodies –Monitoring –P fertilisation advice –P application standards When targeting agricultural P application: P gift should be adapted to soil P concentration and crop demand –Sound fertilisation advice –Differentiated application standards Soil P concentration yield target zone P loss

Thanks for your attention! Institute for Agricultural and Fisheries Research Plant Sciences Unit Agriculture and Fisheries Policy Area Fien Amery Bart Vandecasteele Nutrihort September P P P P P P P