Phytoremediation in Agroforestry

Damase Khasa

Centre for Forest Research and Institute for

Integrative and Systems Biology, Université

Laval, Québec Canada G1V OA6

Presented during the

Soil Remediation Workshop (With special presentation on

Nextgen sequencing), Pretoria, SA, 27 - 28 May 2014

By

Part I: Temperate /subtropical AF

systems

Part II: Potential use of Agroforestry

in phytoremediation

Outline of Presentation

Definitions

Classification of temperate

agroforestry systems

Part I: Temperate AF systems

AF is defined as a dynamic, ecologically based, natural

resources management system that, through the integration of

woody perennials on farms, ranches, and in other landscapes,

diversifies and increases production and promotes social,

economic, and environmental benefits for land users (Orlando

declaration, 02 July 2004).

Agroforestry practices help landowners to diversify products,

markets and farm income; improve soil and water quality;

sequester carbon, and reduce erosion, non-point source pollution

and damage due to flooding; and mitigate climate change.

Definition of AF

- Forest Farming Systems

- Windbreak Systems

- Silvopastoral Systems

- Integrated Riparian Management Systems

- Intercropping Systems

I. Temperate/subtropical Agroforestry Systems

Forest Farming systems

Mycoforestry:

cultivation of edible mushrooms in

woodlots

Fruitiforestry: Cultivation of plants bearing

edible fruits

• e.g., blueberries, cranberries, etc..

Cultivation of blueberries in managed

forest

Quebec is the only one Canadian province experimenting this concept

Advantages:

• windbreaks

• Temperature buffer effect

• Reduction of soil erosion and flowers frost

Source: MRNF 2006

Pharmacoforestry: Cultivation of medicinal

plants

e.g., name "ginseng" is used to refer to both

American (Panax quinquefolius) and Asian or

Korean ginseng (Panax ginseng)

Herboforestry: Cultivation of ornemental, aromatic

and edible herbs

• (e.g., Ferns, Sweet Gale - Myrica Gale, Labrador

Tea, Ledum groenlandicum )

II. Windbreak Systems

11

Source : www2.sbf.ulaval.ca

III. Silvopastoral Systems

IV. Integrated Riparian Management Systems

Benefits of Streambank Reforestation

- Control erosion

- Nutrient filtering

- Shading effects on streams /

modification of aquatic habitat

- Food for invertebrates

- Enhance stream denitrification

- Wood production

- Wildlife corridors

- Carbon sequestration (4-5

ODT ha y-1 biomass)

v) Intercropping Systems

Forestry Control (without crop) AgroForestry (poplars with

soybean crop)

AFFC

OLD field with a LOW [P] content (Université Laval

research site)

8 m 8 m

Riparian buffer systems

Intercropping systems

Woodlot management/soil sanitation

short rotation woody crop (SRWC) fallow

systems

Part II: Potential use of Agroforestry in

phytoremediation

Riparian buffer Systems/Areas

•Riparian areas are parts of the landscape that are strongly influenced by water•Periodic flooding, erosion, sediment deposition, alterations by wildlife

•Agricultural operations, waste disposal, discharge of effluents, grazing, vegetation removal

Nitrogen and

Phosphorus

• N and P: two of the main nutrients

of environmental concern

• In surface water eutrophication

and groundwater

contamination

Lake Winnipeg

Types of Ag

BMPs

Mitigative

BMPs

Constructed wetlands and ponds

Cover crops

Tailwater treatment

Grassed waterways

Vegetative ditches

Vegetative filter strips (VFS)

Field borders / margins

Contour strips

Windbreaks / HedgerowsVegetative

buffers

Riparian buffers

Vegetative

waterways

Edge-of-field

buffers

Conservation tillage

Polyacrylamide (PAM)

Landguard

Smart sprayer technology

Preventative

BMPs

Integrated Pest Management (IPM)

Proper pesticide mixing and loading

Pesticide reformulation

Fertilizer/pesticide

application

management

Monitoring soil nutrient level

Source: Zhang 2009

Riparian buffer

Hillside contour

Hedgerow field-border

Vegetative filter strip

Windbreak

Grassed Waterway Vegetated ditch

Tailwater pond

PAM

Main functions: Slow runoff, Increase infiltration, Trap pollutants (Zhang 2009)

Figure 3. The traditional three zone riparian buffer.

Source: Reprinted, with permission, from Schultz et al. (2000). © ˜2000 by American Society of Agronomy

Riparian buffers

Multi-species vegetation established at the interface between

croplands and surface-water to remove sediments and chemical

pollutants in run-off and shallow water from agricultural land.

• Filtration zone for streams and lakes

• Effective in controlling run-off erosion

• Preserve biodiversity (wildlife & aquatic species)

• The success of riparian buffers for phytoremediation depends on

the species used

• Examples

1. Poplars and forage grasses in multi-species buffer zones phytoremediate

atrazine and phosphorus (Chang et al. 2005; Lin et al. 2008; Kovar and

Claassen, 2009).

2. Willow cultivars tend to promote some bacterial groups and early

ectomycorrhizal species (Pezizomycetes, Sphaerosporella brunnea) in

hydrocarbons (HC) contaminated soils (Bell, Hassan et al.2014).

3. Panicum virgatum L. a grass that is grown on riparian buffer systems has a

good potential to uptake, degrade and detoxify atrazine in the rhizosphere

(Lin et al., 2008).

4. Tree species in riparian buffer zones in Peninsular Malaysia produced a

large amount of woody biomass and substantially removed sediments in

channels leading into headwater streams (Gomi et al. 2006).

5. Bamboo ( Bambusa vulgaris), a non-timber forest product valued in

handicraft, is grown in tropical riparian zones.

Riparian buffers

Riparian buffers

The phytoremediation property of vegetative grasses involves many

processes (Lin et al. 2005; Dosskey et al. 2010) :

–Soil microbial activities for herbicide degradation

–Denitrification of groundwater

–Phytostabilisation, phytoextraction, rhizodegradation

–Nutrient uptake by fast-growing species.

N cycling in a monocrop

N cycling in a tree/crop intercropping

system

Short-rotation woody crop woodlot

system or soil sanitation fallow

Utilization of fast-growing trees with metal-extraction potential

including poplars, eucalypts, bamboos and N-fixing trees to

remediate contaminated soils.

• Ameliorate degraded soils

• Extract and accumulate contaminants (only at low level)

• Can create soil water deficit

• Examples

Short-rotation woody crop

system

1. Poplars and eucalypts

• Poplar-based agroforestry systems are common in India (Das and

Chatuverdi, 2005).

• Eucalypts are used as fast-growing shade trees in coffee

plantations in the tropics (Schaller et al. 2003).

• Eucalyptus spp. and Populus spp. that are cultivated at close

spacing for rotations of 10 years or less can be used in

phytoremediation (Rockwood et al. 2004).

2. Bamboos (presentation by Mr. Jan Van Zyl)

3. N-fixing trees such Acacias, Casuarinas, Leuacaenas

Alley cropping/intercropping

systems

1. Fast-growing nitrogen-fixing species

• Acacia angustissima, Acacia mangium, Inga edulis and Albizia sp.

are used in alley cropping in the tropics.

• Have potential for heavy-metal extraction and accumulation.

• However, less is known on the phytoremediation potential of alley

cropping.

• More work needs to be done to to identify systems that have a

large potential for phytoremediation, while providing local people

with food and other benefits.

Hydraulic lift

Plant roots can redistribute water from wet zones deeper in the soil, to

dry soil zones close to the surface in dry regions, a process known as

hydraulic lift (Richards and Caldwell 1987).

Deep roots absorb water when transpiration is high during the day,

and re-distribute the absorbed water to the rhizosphere in drier layers

when plant transpiration is low (at night). Figure.

Hydraulic lift

Phenomenon used in agroforestry for water redistribution between woody

species and crops, and to assist in phytoremediation of contaminated soils.

Rewetting the rhizosphere in the shallow soil layers :

–Keeps microbes active for biodegradation of organic chemicals in soils.

–keeps fine roots wet, which facilitates the absorption of pollutants by

roots.

–Enhances the release of chemicals, thereby facilitating their acquisition

by hyperaccumulators (or metallophytes) (Liste and White 2008).

Hydraulic lift

Examples :

–Acacia tortilis (Ludwig et al. 2003; Dhillon et al. 2008), Eucalyptus (Bafeel 2008;

Caldwell et al.1998; Hamada et al. 2003), Dalbergia sissoo, Melia azedarach,

Morus alba, poplars, Szygium cumini and Terminalia arjuna (Dhillon et

al. 2008) have been found to phytoremediate contaminated soils that

benefit from hydraulic lift.

Next steps

• Much more research is needed to understand the phytoremediation

potential of agroforestry systems especially in mining areas to secure food

security for local people

• For example:

*design agroforestry systems that minimize competition for water

while favoring hydraulic lift.

*assessment of decontamination potential of agroforestry tree and

shrub species for polluted soils.

*include phytoremediation potential in the criteria of tree selection

for introduction in agricultural landscapes

*more work should be done on the phytoremediation properties of

the association between agroforestry species and microsymbionts

on contaminated soils by either organic or inorganic compounds

AF at Université Laval

Unique in Canada !

Since 1997, formal M.Sc (48

credits including internship in tropical

or temperate AF (unique in Canada)

PhD sur mesure also possible

Within and between collaborations

(U. Moncton, U. Guelph, U.

Saskatchewan, U. Alberta, PFRA)

MOUs (CATIE, WAC, CIFOR)

New textbook published

37

Members of the

Biomonitoring and

Remediation Groups, EME,

NRC-Montreal

Acknowledgements

Funding

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Acknowledgements

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THANK YOU

VERY MUCH FOR

YOUR ATTENTION