soil degradation by intensive uk agriculture and how to ... · mycorhizasoil ley- 10% increase in...
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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
mb
ers
of
sam
ple
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
Wei
ght
of
aggr
egat
es p
er 1
00
g d
ry s
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
ggin
g
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.