Rothamsted Researchwhere knowledge grows

Rothamsted Researchwhere knowledge grows

Dr Jennifer DungaitCIAT-Colombia

30 09 15

Soil Organic Carbon – devising a single proxy measure for the

sustainability of pastoral systems

Broom’s Barn (1987)

North Wyke (2009)

Harpenden (1843)

Rothamsted Research in 2015

North Wyke Farm Platform

Global Farm Platform Partners and Farms

http://www.globalfarmplatform.org/

Soil Organic Carbon – devising a single proxy measure for the sustainability of pastoral systems

Global Farm Platform Priority: Soil Health

Global data set to reveal the relationships between SOC and soil health and plant productivity and quality.

A global network of sites with a suite of management practices that can improve soil health (SOC).

Sustainable ruminant livestock systems that are resilient to change

Rothamsted Researchwhere knowledge grows

Rothamsted Researchwhere knowledge grows

Agriculture is the ‘largest threat to biodiversity and ecosystem function of any single human activity’.Millenium Ecosystem Assessment (2005)

Agriculture and soil degradation

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1850 1875 1900 1925 1950 1975 2000

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Unmanured continuous wheat =

Introduction of new wheat variety

fallowingliming

herbicidesfungicides

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Introduction of new farming practice

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Continuous wheat:FYM =PK + 144 kg N =

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1st wheat in rotation:FYM + spring N =Best NPK fertiliser =

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Potential yieldincrease?

SOMmanagement

More effectiveBroadbalk Classical Experiment

YIELD GAP

Dungait et al. (2012). Advances in the understanding of nutrient dynamics and management in UK agriculture. Science of the Total Environment 434, 39-50.

Managing soils to close the yield gap?

Carbon – the friendly element!

Soil organic matter (SOM) contains:• Soil organic carbon

(SOC) (57%)• Nitrogen• Phosphorus• Sulphur• Microelements

Dungait et al. (2012) Advances in the understanding of nutrient dynamics and management in UK agriculture. Science of the Total Environment 434, 39-50.

WHY increase SOC?

Acknowledgements: Rattan Lal

FASTFASTFAST Variables

SLOW Variables

SOC increase needs patience!

Carpenter & Turner (2000) Hares and tortoises: Interactions of fast and slow variables in ecosystems. Ecosystems 3, 495-497.

Rapidly-cyclingEasily accessibleGoal-oriented

Slow-cyclingLess obviousUnderlying

WHAT is SOC?

Mostly decomposed plant Soil microorganisms <5%

HOW to increase SOC

Increase inputs- Land use change (arable to perennial crops)- Increase carbon in subsoils

Kell (2011) Breeding crop plants with deep roots: their role in sustainable carbon, nutrient and water sequestration. Annals of Botany 108, 407-418.

Increase perennial plants

Fibre, forage and food AND

carbon storage

FORAGE GRASS PERENNIAL GRAINS?

Glover et al. (2010) Increased food and ecosystem security via perennial grains. Science 328, 1638-1639.

2013 Festulolium cv PriorLolium perenne x Festuca pratensis

Designing grasses for ecosystem services

Forage productionFlood alleviationDrought resistance Carbon sequestration in subsoils

Root biomarkers

w-hydroxycarboxylic acids

a,ω-hydroxycarboxylic acids

Quantifying root inputs

Core

HOOH

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Mendez-Millan et al. (2010) Molecular dynamics of shoot vs. root biomarkers in an agricultural soil estimated by natural abundance 13C labelling. Soil Biology and Biochemistry 42, 169-177.

How to increase SOC

Increase inputs- Land use change (arable to perennial crops)- Increase carbon in subsoils- Organic amendments (manures and biosolids)

CAUTION! Pollution swapping!

C3

C40 – 23 cm

0 – 5 cm

Recalcitrant?

How does manure increase SOC?

Dungait et al. (2005) Quantification of dung carbon incorporation in a temperate grassland soil following spring application using bulk stable carbon isotope determinations. Isotopes in Environmental and Health Studies 41, 3-11.

Is lignin recalcitrant in soil?

Dungait et al. (2008) Off-line pyrolysis and compound-specific stable carbon isotope analysis of lignin moieties: a new method for determining the fate of lignin residues in soil. Rapid Communications in Mass Spectrometry 22, 1631-1639.

Large decreases in lignin abundance after 1 year

Lignin decomposition is monomer-specific

Increase recalcitrant SOC??

Dungait et al. (2012) Soil organic matter turnover is governed by accessibility not recalcitrance. Global Change Biology 18, 1781-1796.

Increase inputs- Land use change (arable to perennial crops)- Increase carbon in subsoils- Organic amendments (manures and biosolids)

Reduce losses- Reduced tillage (green mulches and crop residues)

HOW to increase SOC

Soil organic carbon: 0.93%

Soil organic carbon: 2.65%Conventional tillage (CT)

No till (NT100)

Herbicide resistant maize (‘Liberty-link’)

SOC and drought resistant

Min tillage: increases SOC, reduces losses

Beniston et al. (2015) Carbon and macronutrient losses during accelerated erosion under different tillage and residue management. European Journal of Soil Science 66, 218-225.

More new, soil carbon under no till (NT100)

Less soil lost under no till (NT100) – all new

More older, soil carbon lost from conventional till (CT)

Old carbon (>40 years)

New carbon (<40 years)

Reduce losses- Reduced tillage (green mulches and crop residues)- Reduce leaching of DOC- Reduce erosion

HOW to increase SOC

Lignin in leachates from soils

Williams et al. (2015) Contrasting temperature responses of dissolved organic carbon and phenols leached from soils. Plant and Soil, 1-15. doi.org/10.1007/s11104-015-2678-z

Lignin monomers – biomarkers of terrestrial vegetation

Direct correlation between total dissolved organic carbon (DOC) loss from soils

Weak relationship with phenol loss from soils

Catchment scale researchCATCHMENT SCALE (KM)

Collins et al. (2013) Catchment source contributions to the sediment-bound organic matter degrading salmonid spawning gravels in a lowland river, southern England. Science of the Total Environment 456, 181-195.

Bulk stable isotopes can be evidence of SOC transport at the catchment scale

Biomarkers for different plant species

n-C27 represent trees and shrubs

n-C29/31 are the predominant chain lengths in many (but not all) grasses

Sphagnum be typified by n-C23 and n-C25 alkanes

n-alkane = straight chain

Puttock et al. (2014) Woody plant encroachment into grasslands leads to accelerated erosion of previously stable organic carbon from dryland soils. JGR: Biogeosciences 119, 2345-2357.Norris et al. (2013) Biomarkers of novel ecosystem development in boreal forest soils. Organic Geochemistry 64, 9-18.

n-C29 dominantGRASS

n-C27 dominantWOODY

Source of sediment in salmon gravels

PLANTS RIVER SEDIMENTS

Tracking C erosion from maize

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4‰

30% of OC in rivers from maize?

Mean d13C values of n-alkanes (n-C25:n-C31)

Faecal contamination of cress beds

Gill et al. (2010) Archaeol - a biomarker for foregut fermentation in modern and ancient herbivorous mammals? Organic Geochemistry 41, 467-472.

WHAT DOES SOC DO?

More SOC = more microbes

Beniston et al. (2014) Soil organic carbon dynamics 75 years after land-use change in perennial grassland and annual wheat agricultural systems. Biogeochemistry 120, 37-49.

More microbes = more aggregates

Hirsch et al. (2009). Starving the soil of plant inputs for 50 years reduces abundance but not diversity of soil bacterial communities. Soil Biology and Biochemistry 41, 2021-2024.

Arable + grass Control

Soil microbes share carbon

Dungait et al. (2013) The variable response of soil microorganisms to trace concentrations of low molecular weight organic substrates of increasing complexity. Soil Biology and Biochemistry 64, 57-64.

Culture independent methods:Phospholipid fatty acid (PLFA) analysis of soil microbes

• Phospholipids are major components of cell walls

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• Phospholipids short-lived upon cell death• PLFAs represent living microbes

Phospholipid

Phospholipid fatty acids (PLFAs)

Chemical release_

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Phospholipid fatty acids (PLFA)

Earthworms share carbon

Bacteria Plants/fungi de novo

Dungait et al. (2008) Enhancing the understanding of earthworm feeding behaviour via the use of fatty acid d13C values determined by gas chromatography-combustion-isotope ratio mass spectrometry. Rapid Communications in Mass Spectrometry 22, 1643-1652.

Management changes microbial responses to temperature change

EnhancementCompensation

Soil microbial response to temperature change is absent or negative in low C managed soils!

Karhu et al. (2014) Temperature sensitivity of soil respiration rates enhanced by microbial community response. Nature 513, 81-84.

Global decomposition transect

n-alkanes from plant waxes

Carbohydrates from plant cell walls and microbes

Lignin from plant cell walls

• Processes in soils are very difficult to study because the soil is a ‘black box’, and a complex matrix with multiple physical, biological and chemical variables.

• Biogeochemical approaches can help to reveal pathways of transformation and transport that are sometimes counter-intuitive.

• The effect of climatic variables (temperature and rainfall) on soil processes and how they will change as the human population grows must be considered to achieve sustainable agriculture.

Conclusions

Acknowledgments

THANK YOU

SOC: We should not ‘hoard it’, we should ‘use it’! Janzen, 2006