phosphorus regulations of the nitrates directive what is the scientific basis ?

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

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

Phosphorus Regulations of the Nitrates Directive

What is the scientific basis ?

Page 2: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Overview of presentation1. 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

Page 3: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Monitoring water qualityWater quality in Ireland is monitored by the

Environmental Protection Agency

Latest report: Lucey et al., 2006.

Page 4: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Rivers

Page 5: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

RiversCauses of serious pollution

Source: Toner et al., 2005.

Page 6: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

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.

Page 7: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

RiversWhat 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

Page 8: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

GroundwaterDistribution of nitrate concentrations

Page 9: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Estuarine waters

Source: Lucey et al., 2006.

Page 10: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Summary

1. Surface waters: rivers and lakesMain concern: eutrophication (phosphorus)

2. GroundwaterMain concern: drinking water quality (nitrogen)

3. Estuarine waterMain concern: eutrophication(nitrogen & phosphorus)

Page 11: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Index 4Index 1 Index 2 Index 3

0 3 6 10

Teagasc P-research

1. Build up P soil reserves to Target IndexTarget 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

Ris

k of

P-lo

ss

Page 12: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Teagasc P-research

Resulted in large reduction in P-fertiliser use,without loss of productivity

P-Advice 1997:

35

40

45

50

55

60

65

'94 '95 '96 '97 '98 '99 '00 '01 '02 ,03 '04 '05

Year

Ch

emic

al

fert

ilis

er P

use

*10

00 t Frequency distribution of soil test P

0

5

10

15

20

25

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 >10Soil Test P (Morgan's) (mg/l)

per

cen

tag

e o

f so

il

sam

ple

s

Index 1: 15% Index 2: 36% Index 3: 25%Index 4:

23%

Page 13: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Teagasc P-research

Agronomic:

Do different soils need different P-advice ?

New P-research

Environmental:

Do different soils show different risks of P-loss ?

Page 14: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

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 Morgan’s extractant

Soil P Index Soil test P (mg l-1) Description

1 0.0 – 3.0 P-deficiency

2 3.1 – 6.0 Target Index: no early grass, herbage not fully utilised

3 6.1 – 10.0 Target Index: early grass, full herbage utilisation

4 > 10.0 No further response to P-fertiliser

Source: Coulter et al., 2004

P-Index:

Page 15: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Agronomic P-researchFine-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 dietsUp to 4 g kg-1 P required in herbageP-concentration response ≠ Herbage yield responseMorton et al. (1999); Quintero et al. (2003)

3. 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)

4. Differences between soils?

Page 16: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

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

Page 17: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Objectives

1. Quantify herbage yield and herbage P-content as functions of:- soil-test P- fertiliser Pfor a range of contrasting soils;

2. 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;

Page 18: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Materials & MethodsLay-out:

• Eight soil series / associations:

Classification and selected characteristics of the soils used in this study (Brennan, 2002; Herlihy et al., 2004). Series/association No. Principle soil Parent material Drainage pH range Location Association-13

13 Acid brown eaths Sandstone-limestone diamicton Good 5.0-6.4 Waterford

Clonroche

14 Acid brown eaths Ordovician shale diamicton Good 5.8-6.5 Wexford

Association-15

15 Brown Podzolics Sanstone-shale diamicton Good 5.7-6.6 Cork

Castlecomer

22 Gleys Upper Carboniferous (Silesian) shale diamicton

Poor 5.2-6.0 Kilkenny

Baggotstown

30 Grey brown podzolics Calcareous fluvio-glacial gravel

Good 5.6-6.9 Offaly

Kinvarra

33 Shallow brown earths and rendzinas

Limestone diamicton (shallow) Good 5.6-7.3 Galway

Elton

34 minimal grey brown podzolics Limestone diamicton Good 4.8-6.5 Tipperary

Howardstown

39 gleys Limestone diamicton Poor 4.9-6.3 Limerick

Source: Gardiner and Radford (1980)

• 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.

Page 19: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

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, …)

Page 20: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Materials & MethodsAnalysis:

• 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):

M

i

F

ii

K

M

K

FYY

1

1

1

11max,

Page 21: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Materials & Methods

M

i

F

ii

K

M

K

FYY

1

1

1

11max,

M = <<

M = >>

Y

F

M = <<

M = >>

Y

F

Y

M

F = <<

F = >>

Y

M

F = <<

F = >>

Page 22: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

ResultsP-concentration

Soil 13

Soil 14

Page 23: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

ResultsP-concentration

Soil 30

Soil 39

Page 24: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

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)

Page 25: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

P - requirementsYield criterion:criterion: 95% of potential yield

0

10

20

30

40

50

60

70

80

90

1 2 3Soil P Index

P f

erti

liser

req

uir

emen

t(k

g /

ha)

Soil13

Soil14

Soil15

Soil22

Soil30

Soil33

Soil34

Soil39

criterion: herbage P-content of 3 g/kg

0

10

20

30

40

50

60

70

80

90

1 2 3Soil P Index

P f

erti

liser

req

uir

emen

t(k

g /

ha)

criterion: herbage P-content of 3.5 g/kg

0

10

20

30

40

50

60

70

80

90

1 2 3Soil P Index

P f

erti

liser

req

uir

emen

t(k

g /

ha)

P-concentration criterion:

Page 26: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Agronomic P-researchResults:

1. Yields:Target Index 2 adequate for 7 out of 8 soils

0 3 6 10 Index 4Index 1 Index 2 Index 3 soil P

Yield

Page 27: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Agronomic P-researchResults:

2. Herbage P-content:Low - medium (0.30% - 0.35% P):Target Index 2 for all soils

Medium – high (0.35% - 0.40% P):Low Target Index 2 inadequateHigh Index 2 – Low Index 3 required

0 3 6 10 Index 4Index 1 Index 2 Index 3 soil P

Yield

Lo P

Hi P

Page 28: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Agronomic P-researchResults:

3. Ryegrass and white clover:At least high Index 2 required

0 3 6 10 Index 4Index 1 Index 2 Index 3 soil P

Yield

Lo P

Hi P

clover

Page 29: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

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 yieldQuintero et al. (2003): wheatMorton 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:

Page 30: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-researchEnvironmental Research:

1. Laboratory

2. Field

3. Catchment

Page 31: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-researchConcept:

1. P tied to soil particles (top cms): “sorption”

PP

P

Page 32: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-researchConcept:

1. P tied to soil particles (top cms): “sorption”

2. Reversible: available for plant uptake “desorption”

PP

P

Page 33: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-researchConcept:

PPP

1. P tied to soil particles (top cms): “sorption”

2. Reversible: available for plant uptake “desorption”

3. Loss through overland flow (rainstorm events)

Page 34: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-research2 main factors:

P

P

1. Soil P status

P PP

P

P

P

PPP

Low risk High risk

Page 35: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-research2 main factors:

P

P

1. Soil P status

2. Drainage pathway: infiltration v overland flow

P P

P

Low risk High risk

P P

Page 36: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-researchResults:

1. Well-drained soils:Losses negligible on Indices 1, 2, 3

0 3 6 10 Index 4Index 1 Index 2 Index 3 soil P

Well-drainedWell-drained

Page 37: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Environmental P-researchResults:

1. Well-drained soils:Losses negligible on Indices 1, 2, 3

2. Poorly-drained soils:Losses negligible on Indices 1, 2Risk of P-loss at upper half of Index 3

0 3 6 10 Index 4Index 1 Index 2 Index 3 soil P

Well-drained

Poorly-drained

Well-drained

Page 38: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

New P-regulationsCombining agronomic and environmental results

0 3 6 10 Index 4Index 1 Index 2 Index 3 soil P

Well-drained

Poorly-drained

Well-drainedYield

Lo P

Hi P

clover

Options:

• Different Target Index for different soils

• Change Index system

Page 39: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

New P-regulationsCombining agronomic and environmental results

1. New index 3: Morgan’s 5-8:- max yield- hi P- ok for clover- minimum risk of loss

2. New index 2: Morgan’s 3-5:- max yield- lo P- botanical composition ?

0 3 5 8 Index 4Index 1 Index 2 Index 3 soil P

Well-drained

Poorly-drained

Well-drainedYield

Lo P

Hi P

clover

Page 40: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

New P-regulationsNotes:

1. Only the grassland P index has been changed

2. P-index for tillage remains same

Page 41: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

New P-regulationsPeat:

1. High in organic matter

2. Organic matter blocks build-up

3. Apply maintenance rates only (no index system)

4. Long-term consequences ?

OMOM

OMOM

OMOM

OM

OM

OM

OM

Page 42: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Take home messagesRiver Quality:

• Water quality of rivers is generally good

• 30% affected by eutrophication

• Half attributed to loss from agriculture

Page 43: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Take home messagesEstuaries:

• Concerns about eutrophication

• Only 40% unpolluted

• Contribution from agriculture ?

Page 44: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Take home messagesP 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

Page 45: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Take home messagesP 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

Page 46: Phosphorus Regulations of the Nitrates Directive What is the scientific basis ?

Take home messagesNew P-regulations:

• New Indices:Index 1: 0-3Index 2: 3-5Index 3: 5-8Index 4: >8

• Tillage:No change

• Peat:Maintenance rates only