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

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

Monitoring water qualityWater quality in Ireland is monitored by the

Environmental Protection Agency

Latest report: Lucey et al., 2006.

Rivers

RiversCauses of serious pollution

Source: Toner et al., 2005.

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.

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

GroundwaterDistribution of nitrate concentrations

Estuarine waters

Source: Lucey et al., 2006.

Summary

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

2. GroundwaterMain concern: drinking water quality (nitrogen)

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

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

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%

Teagasc P-research

Agronomic:

Do different soils need different P-advice ?

New P-research

Environmental:

Do different soils show different risks of P-loss ?

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:

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?

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

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;

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.

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, …)

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,

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 = >>

ResultsP-concentration

Soil 13

Soil 14

ResultsP-concentration

Soil 30

Soil 39

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)

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:

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

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

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

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:

Environmental P-researchEnvironmental Research:

1. Laboratory

2. Field

3. Catchment

Environmental P-researchConcept:

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

PP

P

Environmental P-researchConcept:

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

2. Reversible: available for plant uptake “desorption”

PP

P

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)

Environmental P-research2 main factors:

P

P

1. Soil P status

P PP

P

P

P

PPP

Low risk High risk

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

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

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

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

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

New P-regulationsNotes:

1. Only the grassland P index has been changed

2. P-index for tillage remains same

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

Take home messagesRiver Quality:

• Water quality of rivers is generally good

• 30% affected by eutrophication

• Half attributed to loss from agriculture

Take home messagesEstuaries:

• Concerns about eutrophication

• Only 40% unpolluted

• Contribution from agriculture ?

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

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

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