Why does soil matter?

Christine Watson

November 2015

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Air

Water

Organicmaterial

Mineral

What is soil made up of?What is soil?

Willie Towers, JHI

“Each soil has had its own history. Like a river, a mountain, a forest, or any natural thing, its present condition is due to the influences of many things and events of the past.” - Charles Kellogg, The Soils That Support Us, 1956

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Why is soil organic matter important for production?

• Source of nutrients• Soil structure – small changes give big effects• Water holding capacity• Cation/anion exchange capacity

Soil organic matter = soil organisms + partially decomposed plant and animal residues

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Soil carbon in Europe

Joint Research Centre,European Commission 2005

Globally, twice as much carbon is stored in soils as is present in the atmosphere. This is both a threat and an opportunity. The threat is land use change. The opportunity is carbon storage. (Smith, 2012)

The world’s cultivated soils have lost 50 to 70 percent of their original carbon stock. (Lal, Ohio State Uni)

Nearly 50% of European soils contain very low levels of SOM (0-2%), which has been caused by agricultural intensification (Quinton et al. 2010)

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Soil biodiversity

• Soil is home to a quarter of our planet's biodiversity which is essential for food security and nutrition

• A single gram of soil may contain millions of individuals and several thousand species of bacteria.

• Soil is alive and it is the soil organisms (big and small) that are the engine

• Soil biodiversity is (generally) not cute!

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Fertiliser &manure

Drainage

Soil structure

Variety

Soil fertilityBiodiversity

Crop rotation

Tillage

Agrochemicals

Soil organic matter

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Impact of crop diversification on soil carbon

McDaniel et al. 2014 Ecological Applications 24: 560–570

Monoculture

Rotation

Rotation + Cover crop

Baseline

+3.6% soil C + 5.3% total N

+8.5% soil C + 12.8% N

20.7% soil microbial biomass

Inter-linkages between soil management, carbon flows and stocks, and crop yield (SMART SOIL project)

Biological ChemicalPhysical

WaterNutrientsHealth

SOILTYPE

CROP GROWTH

CROPYIELD

OTHER ECOSYSTEM

SERVICES

CARBONFLOWS

CARBON STOCKS

CARBONSTORAGE

SOIL FUNCTIONS

SOIL PROPERTIES

MANAGEMENT

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Changes in soil organic carbon content in the plough layer (0–23 cm) in three treatments of the Broadbalk Wheat Experiment at Rothamsted Research, UK.).

Annual treatments are: , no fertilizers or manure applied since 1844; , PKMg plus 144 kg N ha −1 since 1852; , farmyard manure at 35 t ha−1 fresh weight applied since 1885 plus 96 kg N ha−1 since 1968. Data from Rothamsted Research.

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Changing soil organic carbon content

- +

CO2 emission C sequestration

Cover croppingGreen manuresLeysDiverse rotationManures/biosolidsMin tillAgroforestryForage legumes

MonocropsPloughingBurning residuesBare soilResidue removalNegative nutrient balance

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David Atkinson

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Soil degradation

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Trade-offs……great expectations

www.blue-energyco.com

http://www.morrisonconstruction.co.uk/infrastructure/energy

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Some more challenges associated with soil and food security

• Joined-up approaches to soil protection and resource management

• Social acceptability (urban and peri-urban issues) - closing the loop – food waste and sewage

• Technology – precision approaches • Diets……• Fundamental understanding – scientific frontiers• Our ability to adapt to changes and challenges!

- knowledge, technology, policy, ethics, economics…

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• “We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect.” - Aldo Leopold, 1949. A Sand County almanac.

SOIL is a non renewable resource

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