Trace element fluxes linked to organic waste recycling as fertilizing practice: potential risks? Usefulness of long-term field experiments

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Trace element fluxes linked to organic waste recycling as

fertilizing practice: potential risks?

Usefulness of long-term field experiments

S. Houot

1

_{, A. Michaud}

1

_{, C. Resseguier}

1

_{, D. Montenach}

2

_{T. Morvan}

3

_,

F. Feder

4

_{, V. Sappin-Didier}

5

_{, F. Watteau}

6

_{and P. Cambier}

1

1, INRA, Grignon; 2. INRA, Colmar; 3. INRA , Quimper; 4. CIRAD, Dakar Sénégal; 5. INRA, Villenave d’Ornon; 6. CNRS, Vandoeuvre les Nancy, France

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ICOBTE2019 - Nanjing May 2019

Context

• High demand in mineral fertilizers by agriculture (high energy

demand for N, non renewable resources for P and K…

• Soil C storage  mitigation of climate change; organic matter

supports biodiversity in soils but… decrease of organic matter in

many soils.

• Large production of organic wastes (OW) from agriculture

(manures,…), urban activities (treated waste waters, sludges,

biowastes…), industries (sludges, residues….).

• They contain large amounts of nutrients, organic matter  Their

recycling contributes to circular economy : substitution of mineral

fertilizers (already 25% N, 54% P, 71% K), increase of soil organic

matter.

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ICOBTE2019 - Nanjing May 2019

Contaminants

• OW carry contaminants  soil, crop, water contamination?

• Trace elements, organic contaminants, pathogens, genes…

• Regulation (France) : maximum contents, maximum fluxes for 10

years

_{mg/kg MS} _Cd _Cr _Cu _Hg _Ni _Pb _Zn _As _Se

Sludge 10 1000 1000 10 200 800 3000

Composts 3 120 300 2 60 180 600 18 12

• Concentrations tend to

decrease (ex sludge

2000  2014= -10% to

-48% except for Zn

(+7%)

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ICOBTE2019 - Nanjing May 2019

Questions and objectives

• What are the effects of repeated application of OW?

• Are we able to quantify negative impacts on soil functionning?

On crop quality? On water quality?

• Long term experiments with repeated application of different

OW  after 15 to 20 years: which effects ? Negative

impacts? Usefulness for scientists and decision makers?

• Are the actual regulations safe enough?

• Do we have analytical methods to quantify the availability of

TE (bioavailability for crops, mobility towards ground waters)

• Do other TE need to be regulated?

• Can we predict future risks  prevent them through OW

treatment or new regulation?

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ICOBTE2019 - Nanjing May 2019

Network of

long-term field

experiments

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ICOBTE2019 - Nanjing May 2019

Origin (Waste ± treatment)

Soil

Climate

Time

 Multiple effects

 Simultaneous

 Interactions

 Long term?

Crop

OW

Soil

Water

Monitoring in the long-term field

experiments

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France, Ile de France, started in 1998

Loamy soil, temperate climate

Treatments:

Composted sludge (DVB)

Biowaste compost (BIO)

Municipal solid waste compost (OMR) Farmyard manure (FUM)

Control (CN)

Wheat- Maize succession

OW Application:

Every 2 years , 4 t C/ha  2 times usual application rates

QualiAgro site

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Crop

OW

Soil

Water

Examples of monitored data

• _{Organic matter}

• _{N, P, K}

• _{Crop yields (increase)}

• _{N, P, K}

• _{Leached fluxes}

• NO

₃

• _{Organic matter}

• _{N, P, K contents}

• _{pH, CEC}

• _{Biological activities}

• _{Physical properties}

Air

• _GHG

• NH

₃

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ICOBTE2019 - Nanjing May 2019

Crop

OW

Soil

Water

Monitoring of trace elements

• _{Total contents}

• _{EDTA extractable}

• CaCl

₂

extractable

Total contents

• _{Total contents}

• _{Leached fluxes}

• _{Total contents}

• _{EDTA extractable}

• CaCl

₂

extractable

• Evolutions of contents?

• Relation with OW characteristics • Extractable fractions: estimation of mobile and available for crops and ecotox effect?

• Consequences on soil functionning?

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Peltre et al., 2012 ISMO (% C organique) 0 20 40 60 80 100 Autres Digestats Matières animales Engrais Matières végétales Mulchs

Effluents d'élevage avec litière Effluents d'élevage sans litière Composts d'effluents d'élevage Composts urbains Boues 440 MOE Roth C modeling Potential C storage T C. ha-1_year-1 _{(20 years)} dosis 1T C. ha-1_year-1 IROC indicator Scenarios Lashermes et al., 2009 0.17 tC/ha.year :« 4 per 1000 »

Increase in soil organic matter

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2 0 50 100 150 200 250 300 350 a o û -0 5 o ct -0 5 d é c-0 5 fé v-0 6 a v r-0 6 ju in -0 6 a o û -0 6 o ct -0 6 d é c-0 6 fé v-0 7 a v r-0 7 ju in -0 7 a o û -0 7 o ct -0 7 TN T0 MSW GWS a ab b a ab bc c a ab b a ab b a ab b ab a ab b ab épandage épandage

Increase of earthworm population (nber/m2₎ _{Increase in porosity}

OMR _Control

(Capowiez et al., 2009)

ADEME

Increase in biological activity

• Enhanced biological activity

• Modification of microbial biodiversity • No observed adverse effect

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Increase of pH, CEC

CEC

Different efficiencies related to OW characteristics:

• C storage and biological activity : BIO=DVB> FYM>OMR

• CEC: BIO> DVB=FYM=OMR

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13 Cd Cr Cu Hg Ni Pb Zn + 7% BIO - 15% CN ≠ analytical method + 70% DVB + 1% CN + 19% DVB - 31% CN Large variability Variabilité + 8% BIO + 1% CN + 10% OMR - 10% CN + 32% DVB - 3% CN Contents in similar soils in Ile de France

 Significant increase for [Cu] et [Zn]  Not for the other TE

Soil content equivalent to simlar other soils

Evolution of TE contents in soils

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• [Cu, Zn] significant increase  Input fluxes explained the TE stock increase • No differences in crop contents in TE among the treatments

• Small absorption of TE by crops

Increase in total TE contents

explained by OW inputs

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• Comparison between soil contents in 2015 and contents estimated without

risks : <5% of affected microorganisms, taking into account soil properties (pH,

OM…)

Content QualiAgro 2015

(mg kg-1₎ Content calculated without risk_{(mg kg}-1₎

Cd 0,2 (CN) - 0,25 (DVB/BIO) 2,7

Cu 12 (CN) - 20 (DVB) 65 (CN) - 78 (DVB)

Ni 15 41 (CN) - 59 (BIO)

Pb 21 (CN) - 28 (DVB) 182 (CN) - 273 (BIO)

Zn 49 (CN) - 68 (DVB) 112 (CN) - 162 (BIO)

After 15 years and 9 spreading of OW : no potential adverse effects on soil microorganisms

• Indicator Oorts et al. (2018): “Threshold calculator for metals in soils” (Arche consulting)

Which risks for soil biology ?

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CaCl₂ extractable ≈ soluble in water

and mobile

• Small proportions : up to 14% • Larger for Cu and Ni in OMR

EDTA Extractable ≈ complexed to OM

• Larger proportions : up to 50-80% • Largest proportions for Cd, Pb and Zn

Indicators of potential mobile or

available fractions of TE in OW

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Increase in potential available TE

explained by OW inputs in soils

• Increase in EDTA extractable stocks in soils globally explained by OW inputs

• But slope > 1  more available TE?

• Differences among the OW: slope higher with more stable composts

• But no differences in grain contents (plant regulation of absorption?)

Cambier et al., 2018

Zn

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Mobile fraction of TE (CaCl

₂

) in

soils

Cambier et al., 2018 • Mobile fractions larger for Cd, Ni and Zn in control • No relation with OW inputs • Interaction with other effects (pH, OM….)

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ICOBTE2019 - Nanjing May 2019

Soluble fraction of TE (in water)

• pH and Cd contents in water collected from lysimeters

• Interactions between Cd content and water pH

• Cd content increases when pH decreases (control and sludge compost)

pH Cd

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ICOBTE2019 - Nanjing May 2019

Biodiversity Service

Water regulation Nutrient cycling

Soil contamination

Crop production Climate regulation

 All OW improved QI compared to mineral N, except "total contamination"  The BIO compost presented the best scores