Reporting the effect of Cropland
Management on carbon storage in soils
and biomass
Janet Moxley, and Heath Malcolm, CEH, Bush Estate, Penicuik Midlothian, EH26 0QB [email protected]
How cropland is managed affects how much carbon is stored in soil and biomass, and this needs to be quantified to
assess how changing management affects greenhouse gas emissions.
Policy Background
Land management can play a significant role in
mitigating or exacerbating climate change.
Key Management Practices for UK Cropland
Soil
The UK reports emissions and removals of greenhouse
gases from land use and management in the Land Use,
Land Use Change and Forestry inventories which are
prepared following procedures laid down by the
Intergovernmental Panel on Climate Change (IPCC) and
the Kyoto Protocol (KP).
• Cultivated vs set aside vs permanent crop
The UK has elected to include reporting of carbon stock
changes as a result of Cropland Management in its
LULUCF inventory by the end of the second KP
commitment period in 2020. As a result a reporting
system has been developed to allow estimation of
changes in biomass and soil carbon stocks as a result of
changes in Cropland Management.
• Drainage of organic soils
• Inputs of manure, crop residues and fertiliser.
No clear effect found for tillage reduction under UK
conditions.
Biomass
•
Crop type (annual, orchard, shrubby perennial, set
aside and fallow).
Approaches used
• IPCC default emission factors used for cultivated, permanent and
set aside, and for inputs.
Literature search and modelling found no clear effect for tillage
reduction under UK conditions, so emission factor set to reflect
this.
• Equilibrium soil carbon stock of tilled, cultivated land on mineral
soils receiving medium input taken as 150 tC/ha (Bradley et al,
2005)
•
Activity data from Agricultural Census, British Survey of Fertiliser
Practical and Scottish Agricultural Production Methods Survey.
Carbon stock change (tC)
Soil
1,000,000
800,000
600,000
400,000
200,000
0
-200,0001990
-400,000
-600,000
-800,000
-1,000,000
Net change
20 year period to reach equilibrium carbon stock following
change.
Biomass
• Biomass carbon stocks of different crop types assessed from UK
and international literature.
•
Areas under different crops taken from Agricultural census data.
• Carbon stock change assumed to happen within the year of land
use change.
1995
2000
Change due to LUC
Change due to CM
2005
2010
Peat Drainage Cropland
Biomass carbon stocks of Scottish Cropland
3,000,000
Carbon stock (tC)
• Total soil carbon stock of Scottish Cropland estimated to be
approximately 95 MtC.
3,500,000
Soil carbon stock change in Scottish Cropland due to land
use and management change.
2,500,000
2,000,000
1,500,000
1,000,000
500,000
0
1990
Annual crop
1995
Orchard
2000
Shrubby perennial crop
2005
SAS and fallow
2010
Total
Conclusions
Issues for future improvement
• Change in the soil and biomass carbon stocks of Cropland is predominantly due to land use change.
• Change in soil and biomass carbon stocks due to change in Cropland management is predominantly due to
changing proportions of set aside and fallow land and annual crops.
• There is limited scope to store more carbon in Cropland soils and biomass, as widespread change to
permanent crops would not be practical. Increased use of manure and fertiliser could increase soil carbon
stocks, but would have to be balanced against increased nitrous oxide emissions and nitrate run off.
Use of spatially explicit data (IACS, CORINE) to improve
tracking of land use change.
Wider consideration of the effects of soil drainage and
rewetting will be needed to reflect IPCC Wetland
Supplement Guidance.
References Bradley,, R.I et al (2005), A. A soil and carbon database for the United Kingdom. Soil Use and Management, 21 363- 369.
Moxley, J et al.(2014a) Capturing Cropland and Grassland Management Impacts on Soil Carbon in the UK LULUCF Inventory Contract Report prepared for the Department for Environment, Food and
Rural Affairs Project SP1113.
Moxley, J et al Capturing the effect of Cropland and Grassland Management on biomass carbon stocks in the UK LULUCF inventory. Unpublished report by CEH for Department of Energy and Climate
Change contract TRN265/09/2011 (2014b)
Funding from Defra (SP1113) and DECC (TRN265/09/2011) is gratefully acknowledged.
WHY DO WE NEED TO KNOW HOW LAND
MANAGEMENT AFFECTS CARBON STOCKS?
BECAUSE IT SHOWS US HOW POLICIES TO TACKLE
CLIMATE CHANGE ARE WORKING, AND ALLOWS US TO
MEET INTERNATIONAL REPORTING REQUIREMENTS.