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

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Presentation on theme: "Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?"— Presentation transcript:

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

2 Overview of presentation 1. Water quality in Ireland Rivers Groundwater Estuaries Summary 2.Teagasc P-research Historic research Agronomic research Environmental Research 3. New P-regulations New Index System Note on tillage Peat

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

4 Rivers

5 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 was suspected 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 1.Surface waters: rivers and lakes Main concern: eutrophication (phosphorus) 2.Groundwater Main concern: drinking water quality (nitrogen) 3.Estuarine water Main concern: eutrophication (nitrogen & phosphorus)

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

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

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

14 Agronomic P-research P-advice: 1.Build up soil P reserves to target index (either 2 or 3); 2.Maintain Soil Test P at target index by replacing offtakes in milk and meat. The Irish P-index system for mineral soils using Morgans extractant Soil P IndexSoil test P (mg l -1 )Description 10.0 – 3.0P-deficiency 23.1 – 6.0Target Index: no early grass, herbage not fully utilised 36.1 – 10.0Target Index: early grass, full herbage utilisation 4> 10.0No further response to P-fertiliser Source: Coulter et al., 2004 P-Index:

15 Agronomic P-research Fine-tuning P-advice: 1.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 2.Dietary P-requirements of grazing ruminants: Drive towards grass-only diets Up to 4 g kg -1 P required in herbage P-concentration response Herbage yield response Morton et al. (1999); Quintero et al. (2003) 3.Positive relationship between Soil Test P and P loss to water Sharpley 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) 4.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 Association-13 Clonroche Association-15 Castlecomer Baggotstown Kinvarra Elton Howardstown Publications: Herlihy et al., 2004 Herlihy et al., 2006 Herlihy & McGrath, 2006 Herlihy & McCarthy, 2006 Schulte & Herlihy, 2007

17 Objectives 1.Quantify herbage yield and herbage P-content as functions of: - soil-test P - fertiliser P for a range of contrasting soils; 2.Establish fertiliser rates required to produce: - 95% of potential yield - a range of herbage P-contents for 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 ( ); plots re-randomised each year on different location within each site.

19 Materials & Methods Measurements: Soil samples: - spring and autumn - 10 cm - Morgans 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 < ) 73 % of variation (59 % - 86 %) explained by STP, fertiliser and year Herbage Yield: All regressions significant (p < ) 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 factors e.g. Bailey (2000); Burke et al. (2004)

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

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

27 Agronomic P-research Results: 2.Herbage P-content: Low - medium (0.30% % P): Target Index 2 for all soils Medium – high (0.35% % P): Low Target Index 2 inadequate High Index 2 – Low Index 3 required Index 4Index 1Index 2Index 3 soil P Yield Lo P Hi P

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

29 Implications 1.P-requirements correspond largely to P-rates advised by Coulter et al. (2004) (Green Book) 2.P-requirements dictated by herbage P-concentration: P-concentration of 3.5 g kg -1 guarantees 95% of potential yield Quintero et al. (2003): wheat Morton et al. (1990): grass 3.P-requirements largely similar across soils, except for soil 22: Castlecomer = poorly-drained, high OM-content 4.[P] is easily measured in first cut silage ~ annual average Implications for fertiliser advice:

30 Environmental P-research Environmental Research: 1.Laboratory 2.Field 3.Catchment

31 Environmental P-research Concept: 1.P tied to soil particles (top cms): sorption P P P

32 Environmental P-research Concept: 1.P tied to soil particles (top cms): sorption 2.Reversible: available for plant uptake desorption P P P

33 Environmental P-research Concept: P P P 1.P tied to soil particles (top cms): sorption 2.Reversible: available for plant uptake desorption 3.Loss through overland flow (rainstorm events)

34 Environmental P-research 2 main factors: P P 1.Soil P status P P P P P P P PP Low riskHigh risk

35 Environmental P-research 2 main factors: P P 1.Soil P status 2.Drainage pathway: infiltration v overland flow P P P Low riskHigh risk P P

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

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

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

39 New P-regulations Combining agronomic and environmental results 1.New index 3: Morgans 5-8: - max yield - hi P - ok for clover - minimum risk of loss 2.New index 2: Morgans 3-5: - max yield - lo P - botanical composition ? 0358 Index 4Index 1Index 2Index 3 soil P Well-drained Poorly-drained Well-drained Yield Lo P Hi P clover

40 New P-regulations Notes: 1.Only the grassland P index has been changed 2.P-index for tillage remains same

41 New P-regulations Peat: 1.High in organic matter 2.Organic matter blocks build-up 3.Apply maintenance rates only (no index system) 4.Long-term consequences ? P P P OM

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: 0-3 Index 2: 3-5 Index 3: 5-8 Index 4: >8 Tillage: No change Peat: Maintenance rates only


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