Green Week 2012 Nitrates hotspots – prevention and cure Monitoring and modelling nitrogen cycling in rural landscape to mitigate nutrient surface water Chantal GASCUEL-ODOUX

Global Change More Reactive Nitrogen in Environment Nitrogen synthesis & Animal density

N2(g) + 3H2(g) → 2 NH3(g) From Galloway et al. (2003) and J.W. Erisman (2006)

Wor

ld P

opul

atio

n (m

illiar

ds)

Reactive nitrogen (Tg = M

tonnes)

Industriy, transport, Energy

Agriculture

Population

Nitrate Hotspots North Western Europe + regional spots in south

N agricultural input per

agricultural area

N balance per agricultural area

- N surplus - Livestock

& - Effective rainfall

as the main factor controlling N retention

From JRC reports

Surplus Brittany: 2500 kg/km² Seine Basin: 1160 kg/km² Loire Basin: 830 kg/km²

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20

40

60

80

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120

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180

1971

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/02

flux

spéc

ifiqu

es (k

g/ha

/an)

N Fluxes on 30 catchments 60% of the regional drinking water

Increasing trend, then stabilisation High inter-annual variations High variability between catchments

Brittany region, France

Gascuel-Odoux et al., Stoten, 2010

Cattle Surplus

Crop export

Resorption Mineral

Poultry

Pork

Regional N Budget

Total N surplus: 84 800 t

Concentrations in targets regarding drinking water with a high variability

Observed nitrate load(kgN.ha-1.yr-1)

1-BFIN

surplus

[NO3-] aquifer

PS

L

BFI

Bsoil Brain Briparian

Ldgw

R

N retention [0.2 – 1]

specific runoff mean distance to stream hydromorphic soils

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 100 200 300 400 500 600 700 800

flux/surplus vs lame d'eauN flux/Nsurplus versus specific runoff

Specific discharge

N fl

ux/N

surp

lus

Dupas et al., EGU 2012 Nitrogen Workshop 2012

Low retention due to shallow aquifer and short stream network

flux

• Drinking water: 50 mg/l • Intensive agriculture

• Vulnerable ecosystem: around 10 mg/l

Targets

Current mitigation measures

Manure treatment 35 000t / 84 000 t Manure transport (local to regional)

Wetland management Buffer in landscape

– Fertilisation plan at farm level – Upper limit: 210 Kg N/ha/year, 170 of organic N – Closing period (manure spreading) – Spatial restrictions (high slopes, saturated conditions) – Vegetation cover in winter - Grass strip along rivers

Current Regulation

Mitigation at farm level

-

outcome : Catchment Nitrate notation

Reduction in wet areas

= Catc

hmen

t

=

N leaching estimation per rotation type (optimized fertilization)

Environment Sensitivity : soil depth x water drainage x

+

N leaching estimation with real fertilization

+

x

x n fields

8

Dilution by non agricultural areas (woods, urban areas…)

Designing new mitigation options – Territ’eau

Participative diagnostic tool BRETAGNE

http://agro-transfert-bretagne.univ-rennes1.fr/Territ_eau/

N leaching references under some rotations (equilibrium fertilization) from Agrotransfert TERRIT’EAU 2010, drainage > 400 mm)

CC : catch crop, undersown or sow before 1st oct. Low grazing < 300 LSU.grazing days.ha-1, High grazing > 800 LSU.grazing days.ha-1

Effet destruction

125 100

85 70

60 50

45 40 40

35 30

15 10

Permanent grassland, high LSU/ha

Maize silage / cereal+ CC

permanent grassland extensive grazing

Cut grassland

grassland 9 yrs, extensive grazing, wheat permanent grassland moderate grazing

Maize silage + CC/ maize / cereal+ CC Maize silage / cereal / rape / cereal + CC

grassland 6 yrs, mean LSU/ha /Ms+CC/Ms/wheat Idem but grassland 4 yrs

grassland 6 yrs, high LSU/ha /Ms+CC/Ms/wheat Idem but grassland 4 yrs

Idem renewed every 6 yrs

A starting Point

Environmental, Technical & Social difficulties

• Environmental: water transit time, response time • Technical:

– Organic fertilisation (various organic products, farm plot plan ) – High mineralisation in autumn and winter (50-100 kg/ha) – Maize / winter wheat rotation (unefficient intercrop) – Grassland in rotation : up to 300 kg/ha after grassland

destruction

• Social and economic: livestock farming, particularly poultry and pork: Heavy infrastructure. Price volatility.

Difficulties

• Drinking water : 50 mg/l • Intensive agriculture • Regulation & Optimization ...changes and time in highly degraded situations

• Vulnerable ecosystem : around 10 mg/l • New agricultural systems :

agroecosystem approach

Targets

Northern Coast

N as main control (Menesguen et al.)

A large set of small coastal catchments Various features: depth, closeness,..

Dramatic effects at local scale: vulnerable to marine eutrophication - Green tides

14 coastal catchments, i.e. 7% of the agriculturals surface area

A human health problem Local high H2S emission

3500 farms, i.e. 10%

KgN.ha-1.total area-1 KgN.ha-1.Agric.area-1

A diversity of situations

Green algae plan Objective: 30% of the « way » to go down to 10 mg/l before 2015 4 projects already accepted. A scientific council to analyze each plan

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10

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juil.

-98

janv

.-99

juil.

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juil.

-00

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-01

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.-07

juil.

-07

janv

.-08

NO

3 (m

g/L)

ddass AEP bvlg aep

Ecosystem health

Drinking water

120 km², 170 farmers 85% animal breeding

70% in agricultural land 50% in grassland

Average conc. 26 mg/l

100

120

140

160

180

200

220

1997 2006

kg N total /ha SAU

Optimization almost achieved

Moreau et al 2012 (Agee)

Disturbing results….

0

10

20

30

40

5019

98

2000

2002

2004

2006

2008

2010

2012

2014

2016

2018

Années

Nitr

ates

rivi

ère

mg/

L

Current situation

Agri. Environ. Measures

« Zero leaching »

objective N control by vegetation

Years

Nitr

ate

Con

c. In

rive

rs m

g/l

Which agriculture in such environment ?

Exports Internal

Fluxes

Inputs

Reduce N input & Increase N internal recycling

Water

Atmosphere

N sorties

- Farm level pratices at risk

- Catchment level Buffer areas

Animal feeding

Animal density Fertilisers Crop Manure

Légumineuses (N fixation)

Animal production strongly linked to C & N soil storage accumulation

Grassland (grazing, storage)

Compléments protéiques

Agroecologic transition in livestock areas

N recycling

N input

N losses

Systemic indicators

Systemic approach

Agroecologic transition

Farms in transition

Systemic modelling

Global input: 100 kg N par ha of agricultural area N mineral + (0,75 ou 0,65) N feed + Δ N organic (export – import)

Feeding animals without risk: 1,40 UGB / ha on grasslands

Include farm constraints in environmental N modelling

CASIMOD’N : Catchment and Agricultural Systems Integrated

MODel for Nitrogen

climate

Biophysical characteristics

of the catchment

Output per catchment map, data series,….

Farm.1 (TF)

strategy

contraints

Agricultural practices

Crop spatial distribution Manure spatial distribution

itk scheduler

Farm.2 (TF)

Farm.n (TF)

Output per farm (yield, …)

Coupling different models : TOURNESOL (Garcia et al., 2005) - FUMIGENE (Chardon et al., 2008) - TNT2 in a plateform RECORD-VLE (Bergez et al., 2009; Quesnel et al., 2009)

N and water catchment

model (TNT2)

19

Systemic models

0

20

40

60

80

100Mineral fertilisation

Organic fertilisation22/18

Grazing 31 / 34

Symbiotic fixation

Deposition

Soil storagevariation 25/21

Crop export

Woodland export

Volatilisation

denitrification

Groundwaterexport 6/2

stream export27/21

Input Output

N Cycling Kg N.ha-1.year-1 Same production N recycling

Different N Lower

N losses

Comparison - 2007 versus - Sytemic approach (two systemic indicators)

• Drinking water • Mitigation and regulation measures

• Vulnerable ecosystem : Conception of new agroecosystems Closing N cyling in landscape But also coherent regulation, specific funding for vulnerable areas, control at plot, farm & catchment level

Hotspots

A L I M E N T A T I O N A G R I C U L T U R E E N V I R O N N E M E N T

Photo G. le Hénaff, UMR SAS

Thank for your attention Chantal.gascuel@rennes.inra.fr Thanks to P. Aurousseau, L. Delaby, P. Durand, R. Dupas, P. Moreau, L. Ruiz, F. Vertes National Agency for Research ANR-Systerra – Acassya Project