Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

1. Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

2. Overview of presentation • Water quality in Ireland • Rivers • Groundwater • Estuaries • Summary • Teagasc P-research • Historic research • Agronomic research • Environmental Research • New P-regulations • New Index System • Note on tillage • Peat

3. Monitoring water quality Water quality in Ireland is monitored by theEnvironmental Protection Agency Latest report: Lucey et al., 2006.

4. Rivers

5. Rivers Causes of serious pollution Source: Toner et al., 2005.

6. Rivers Causes of slight and moderate pollution “In regard to the moderate and slight pollution detected in the period, the bulk of this wassuspected to be caused by municipal and agricultural sources in approximately equal measure.” Source: Toner et al., 2005.

7. Rivers What is eutrophication? Nutrients allow algae to grow rapidly While growing, algae produce oxygen Late summer: algae start dying and rotting Rotting consumes oxygen Low oxygen affects fauna

8. Groundwater Distribution of nitrate concentrations

9. Estuarine waters Source: Lucey et al., 2006.

10. Summary • Surface waters: rivers and lakesMain concern: eutrophication (phosphorus) • GroundwaterMain concern: drinking water quality (nitrogen) • Estuarine waterMain concern: eutrophication(nitrogen & phosphorus)

11. Teagasc P-research yield Risk of P-loss Index 1 Index 2 Index 3 Index 4 0 3 6 10 soil P P-Advice 1997: • Build up P soil reserves to Target IndexTarget Index: 2 for extensive, 3 for intensive • Maintain soil P by replacing offtakes • Regular soil P testing for verification

12. Teagasc P-research P-Advice 1997: Resulted in large reduction in P-fertiliser use,without loss of productivity

13. Teagasc P-research New P-research Agronomic: Do different soils need different P-advice ? Environmental: Do different soils show different risks of P-loss ?

14. Agronomic P-research P-Index: P-advice: • Build up soil P reserves to target index (either 2 or 3); • Maintain Soil Test P at target index by replacing offtakes in milk and meat.

15. Agronomic P-research Fine-tuning P-advice: • Interactions between fertiliser efficiency and Soil Test P:Holford et al. (1985); Slaton et al. (2005)Large response to fertiliser in Index 1; no response in Index 4 • Dietary P-requirements of grazing ruminants:Drive towards grass-only dietsUp to 4 g kg-1 P required in herbageP-concentration response ≠ Herbage yield responseMorton et al. (1999); Quintero et al. (2003) • Positive relationship between Soil Test P and P loss to waterSharpley et al. (1981); Pote et al. (1999); Daly et al., (2002); McDowell & Condron (2004); Kurz et al. (2005a); Kurz et al. (2005b); Jordan et al. (2005) • Differences between soils?

16. Agronomic P-research Major research programme 32 sites: 8 representative soils 4 P-Indices per soil 4 years 4 cuts / year 9 fertiliser P treatments / site:0, 10, 20, 30, 40, 50, 60, 75, 100 kg/ha Publications: Herlihy et al., 2004 Herlihy et al., 2006 Herlihy & McGrath, 2006 Herlihy & McCarthy, 2006 Schulte & Herlihy, 2007

17. Objectives • Quantify herbage yield and herbage P-content as functions of:- soil-test P- fertiliser Pfor a range of contrasting soils; • Establish fertiliser rates required to produce:- 95% of potential yield- a range of herbage P-contentsfor each combination of soil series and soil P-index;

18. Materials& Methods Lay-out: • Eight soil series / associations: Four P-indices per soil Within each site: fertiliser P treatments:0, 10, 20, 30, 40, 50, 60, 75 and 100 kg ha-1. Two reps, four for controls Four years (1997-2000); plots re-randomised each year on different location within each site.

19. Materials & Methods Measurements: • Soil samples:- spring and autumn- 10 cm- Morgan’s extract: Soil Test P • Herbage yield (kg DM ha-1) • Herbage P-concentration (g kg-1) • (texture, pH, Hadley Fractions, Al, Fe, botanical composition, …)

20. Materials & Methods Analysis: • Herbage response to STP is non-linear • Herbage response to fertiliser P is non-linear Holford et al. (1985);Cayley and Hannah (1995); Morton et al. (1999); Quintero et al. (2003); Slaton et al. (2005) • Interactions between STP and fertiliser P Slaton et al. (2005) Non-linear multiple regression equation (SAS: NLIN):

21. Materials & Methods

22. Results P-concentration Soil 13 Soil 14

23. Results P-concentration Soil 30 Soil 39

24. Results P-concentrations in herbage: • All regressions significant (p < 0.0001) • 73 % of variation (59 % - 86 %) explained by STP, fertiliser and year Herbage Yield: • All regressions significant (p < 0.0001) • Only 34 % of variation (9 % - 66 %) explained by STP, fertiliser and year Explanation: • STP and Fertiliser P are good predictors of P-uptake by grass. However, nutrient utilisation and herbage production depend on many more factorse.g. Bailey (2000); Burke et al. (2004)

25. P -requirements Yield criterion: P-concentration criterion:

26. Agronomic P-research Yield 0 3 6 10 Index 1 Index 2 Index 3 Index 4 soil P Results: • Yields:Target Index 2 adequate for 7 out of 8 soils

27. Agronomic P-research 0 3 6 10 Index 1 Index 2 Index 3 Index 4 soil P Results: 2. Herbage P-content:Low - medium (0.30% - 0.35% P):Target Index 2 for all soilsMedium – high (0.35% - 0.40% P):Low Target Index 2 inadequateHigh Index 2 – Low Index 3 required Yield Lo P Hi P

28. Agronomic P-research Yield Lo P Hi P clover 0 3 6 10 Index 1 Index 2 Index 3 Index 4 soil P Results: 3. Ryegrass and white clover:At least high Index 2 required

29. Implications • P-requirements correspond largely to P-rates advised by Coulter et al. (2004) (“Green Book”) • P-requirements dictated by herbage P-concentration:P-concentration of 3.5 g kg-1 guarantees 95% of potential yieldQuintero et al. (2003): wheatMorton et al. (1990):grass • P-requirements largely similar across soils, except for soil 22:Castlecomer = poorly-drained, high OM-content • [P] is easily measured in first cut silage ~ annual average Implications for fertiliser advice:

30. Environmental P-research Environmental Research: • Laboratory • Field • Catchment

31. Environmental P-research Concept: • P tied to soil particles (top cms): “sorption” P P P

32. Environmental P-research Concept: • P tied to soil particles (top cms): “sorption” • Reversible: available for plant uptake “desorption” P P P

33. Environmental P-research P Concept: • P tied to soil particles (top cms): “sorption” • Reversible: available for plant uptake “desorption” • Loss through overland flow (rainstorm events) P P

34. Environmental P-research P 2 main factors: • Soil P status Low risk High risk P P P P P P P P P P

35. Environmental P-research 2 main factors: • Soil P status • Drainage pathway: infiltration v overland flow Low risk High risk P P P P P P P

36. Environmental P-research 0 3 6 10 Index 1 Index 2 Index 3 Index 4 soil P Results: • Well-drained soils:Losses negligible on Indices 1, 2, 3 Well-drained Well-drained

37. Environmental P-research 0 3 6 10 Index 1 Index 2 Index 3 Index 4 soil P Results: • Well-drained soils:Losses negligible on Indices 1, 2, 3 • Poorly-drained soils:Losses negligible on Indices 1, 2Risk of P-loss at upper half of Index 3 Well-drained Well-drained Poorly-drained

38. New P-regulations Yield Lo P Hi P clover Index 1 Index 2 Index 3 Index 4 soil P Combining agronomic and environmental results Options: • Different Target Index for different soils • Change Index system Well-drained Well-drained Poorly-drained 0 3 6 10

39. New P-regulations Yield Lo P Hi P clover soil P Combining agronomic and environmental results • New index 3: Morgan’s 5-8:- max yield- hi P- ok for clover- minimum risk of loss • New index 2: Morgan’s 3-5:- max yield- lo P- botanical composition ? Well-drained Well-drained Poorly-drained 0 3 5 8 Index 1 Index 2 Index 3 Index 4

40. New P-regulations Notes: • Only the grassland P index has been changed • P-index for tillage remains same

41. New P-regulations Peat: • High in organic matter • Organic matter blocks build-up • Apply maintenance rates only (no index system) • Long-term consequences ? OM OM OM OM OM OM OM OM OM OM P P P

42. Take home messages River Quality: • Water quality of rivers is generally good • 30% affected by eutrophication • Half attributed to loss from agriculture

43. Take home messages Estuaries: • Concerns about eutrophication • Only 40% unpolluted • Contribution from agriculture ?

44. Take home messages P research (agronomic): • Target Index 2 sufficient for yield • But Target Index 3 needed for high P-content and botanical composition • Few differences between soil types

45. Take home messages P research (environmental): • P-loss depends on Soil P Status and drainage pathway • Well-drained soils: low risk of loss on Index 1, 2, 3 • Poorly-drained soils: risk at upper half of Index 3

46. Take home messages New P-regulations: • New Indices:Index 1: 0-3Index 2: 3-5Index 3: 5-8Index 4: >8 • Tillage:No change • Peat:Maintenance rates only