Soil degradation by intensive UK agriculture and how to reverse it

Jonathan LeakeProfessor of Plant-Soil Interactions

The University of Sheffield

Soil- the foundations of human food systems

Only 30% of the Earth’s surface is land, and only 9% of this area is cultivated with little scope for future expansion.

Tundra

Forests

Deserts

ice

grazing

70% covered with water-

20 x 20 x 20 km = 8000 km3

The supply of water and nutrients from soil to crops in a 15.6 million km2 area (approximately 7800 km3 of topsoil to 0.5 m) is what now largely sustains 7.2 billion humans

UK wheat yield plateaux

(Knight et al., 2012)

Soil degradation by agriculture threatens future food security and resilience to climate change for our increasing global population

Globally-33% of arable topsoil lost to erosion or degradation in the past 40 years (Yang et al., 2003)

Globally soil degradation costs ~ $10 tn p.a., equivalent to· 160% of the global spend on healthcare or education· 540% of global spend on Research and Development

2010, EU-28

Nearly a billion tonnes of soil lost each year in the EU (970 million tonnes).

Arable land is a major contributor to this soil loss.

Around 140 373 km² of EU arable land (an area larger than Greece) suffers erosion rates >5 tonnes ha-1 year-1.

Permanent arable crops suffer average erosion rates approaching 10 tonnes ha-1.

2015

http://ec.europa.eu/eurostat/statistics-explained/index.php/Agri-environmental_indicator_-_soil_erosion

http://www.eld-initiative.org/

How much is soil degradation costing us and who is paying?

•Approx. £1.2 bn cost per year of soil degradation in England and Wales •Mainly due to

Loss of organic content of soils (47%), Compaction (39%) Erosion (12%)Other (2%)

•- 80% of these costs occur off-site and therefore do not directly impact those responsible.

•The findings confirm that soil degradation has implications for a number of key policy areas such as flood risk management and climate change mitigation

Total income from farming in the UK in 2015 was £4bn, less than 0.5% of GDP, but UK farmers, who are less than 1% of the population supplied 60% of our food.

Wood Hedge 2 m 32 mGrassy

strip

Wood-to-Hedge-to-Field bioassay of wheat

(E. Marshall-Harris MBioSci Thesis)

How do we assess soil degradation in arable land? How do we assess soil quality and functions?What benchmarks and measures should we use?How can we restore soil quality?

Hedge Margin 2 m arable 32 m arable

UK Countryside survey 2007 (Emmett et al., 2010)

Loss of organic matter leads to soil compaction

Loss of organic matter leads to loss of water storage capacity

Losing the plot:

soil is a

diminishing

finite resource

Lancrop perform 15,000 soil tests a year in the UK

Nu

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of

sam

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s

The potential roles of leys in soil restoration?

SoilBioHedgeHarnessing hedgerow soil biodiversity for

restoration of arable soil quality and resilience

to climatic extremes and land use changes.

Dr Lisa Norton, Dr Alastair Leake, Dr Felicity Crotty, Dr Matthew Shepherd,Dr Derek Pedley, Dr Emma Sherlock, Dr Wendy Seal

Peter Burgis

.. .

Permanent grassland

Permanent grasslandArable

last ley 1988

GrasslandTo arable in 2009

Arable to grassland in 2012

Arable last ley 1994

SoilBioHedge

MycoRhizaSoil

Connected ley

Unconnected ley with earthworm barrier to 1m

Arable >40 years

2 year ley connected to hedge

2 year ley unconnected to hedge

Hedge 3m 4m 8m 16m 32m 64m

26% > total biomass than arable35% > root biomass than arable

Effect of ley after 2 years:Total wheat biomass (F (2,67) = 7.9, P < 0.001),

Root biomass (F (2,67) = 5.3, P = 0.008

18% > total biomass than arable27% > root biomass than arable

Data and pictures : Erik Button 2017

Restoration of water-stable macroaggregates by leys

Improved soil biology and functioningIncreased infiltration rates, 4% lower bulk density.Earthworm casts up 420% in unconnected and 566% in connected leys.

HedgeLey at 24m

Wheat at 24m

Data: provided by Dr Caibian Huang 2017

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oil

3 year ley- 86% increase in water-stable macroaggregates > 1mmOver 50% recovery to hedge soil values

Effect of permanent arable versus ley to arable converted land on soil biology and hydrology–impacts on wheat resilience to drought and flooding

DroughtWaterlogging

Effects of leys on wheat resilience to drought and waterlogging

Dro

ugh

tW

ate

rlo

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Harnessing fundamental biological and ecosystem science to create more resilient and sustainable farming systems

Soil and rhizosphere interactions for sustainable agri-ecosystems (GFS-SARISA)

MycoRhizaSoilIdentify wheat genotypic traits, in combination with agricultural field practices, which together facilitate rhizosphere organisms to improve soil quality and enhance crop resilience to climatic stress and disease.

Grass-clover Ley

Min. till+ AM

inoculum

Min. till+

carrier

Ploughed+ AM

inoculum

Ploughed+

carrier

6 Wheat lines in 4 replicate blocks, in 4 treatments

2 year ley Fallow

Earthworms in 20 kg of soil

MycoRhizaSoil

Ley- 10% increase in water-holding capacity and 55% increase in water-stable aggregates >1mm comparted to the ploughed soil.

Minimal tillage caused much more modest improvements in soil quality

1. Restored biological functions such as earthworms and mycorrhizal fungi.

2. Improved soil structure- macroaggregates that hold water, nutrients and organic matter and enable deep root growth

3. Improved soil drainage and macropore flows reducing risk of flooding and soil erosion.

4. Increased crop resilience to drought, flood and pests and diseases

Reintroducing leys into rotations in UK arable farming, in combination with zero tillage, may provide an effective way of

restoring soil functions degraded by decades of intensive cultivation.