1 / 27

Soil organic matter in the Rothamsted plots

Soil organic matter in the Rothamsted plots. David Powlson Andy Macdonald, Margaret Glendining, Andy Whitmore, Kevin Coleman, Dudley Christian. Department of Soil Science, and Centre for Soils & Ecosystem Function Rothamsted Research, UK. or ….

aren
Download Presentation

Soil organic matter in the Rothamsted plots

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Soil organic matter in the Rothamsted plots David Powlson Andy Macdonald, Margaret Glendining, Andy Whitmore, Kevin Coleman, Dudley Christian Department of Soil Science, and Centre for Soils & Ecosystem Function Rothamsted Research, UK

  2. or … Is it OK to remove straw from arable land for use as bioenergy? No …. but …. Yes …. but …..

  3. A “perfect storm” : Food security Energy security Climate change Professor John Beddington FRS UK Government Chief Scientific Adviser

  4. Transport Affordability Policies, …. Food security • Nutrients: • Recycling • Fertilizers Food production Management Well functioning soil Soil organic matter

  5. Ways of maintaining SOM in arable cropping • Ley-arable farming – i.e. intermittent pasture • Add crop residues • Add manures or other organic “wastes” ………………………………………………….. • Minimise tillage • small effect, mainly redistribution • but useful to concentrate SOM near surface • Grow plants with larger root input (breeding) • Grow larger crops by using fertilizers (small effect) • Utilise “black carbon” or biochar?

  6. So appropriate to be cautious about residue removal But …. • 50% of above-ground residues returned to soil in stubble + chaff (winter wheat, UK conditions) • 1.9 t C/ha returned (stubble, chaff, roots, exudates) even when straw is removed (calculated from Broadbalk data)

  7. Total SOM content changes between different equilibrium levels …. slowly Long term experiments – Valuable to quantify changes caused by different managements Increase inputs (or slow down decomposition) Final Equilibrium Soil C Content In practice (non-experimental situations) – Equilibrium rarely achieved; one management change superimposed on another Transition Initial Equilibrium Time

  8. Straw removed in all treatments

  9. Broadbalk • Winter wheat • (continuous & rotation) • Started 1843

  10. Straw incorporated in one section since ???? • But this section also has higher clay content than rest of field • Difficult to resolve effects

  11. Results from Roth and Woburn straw expts

  12. Even if changes in total SOC are small/slow, changes in specific fractions may be occurring.

  13. Straw incorporation experiment, Denmark (18 years, spring barley) 40% increase in microbial biomass No measurable effect on soil total C or N Powlson et al (1987) Soil Biology & Biochemistry18, 159-164

  14. Can a small change in SOM have large effects on soil properties?

  15. Draught Forces & Energy Strain gauged frame (to measure draught forces) Doppler radar sensor (forward speed) Laser proximity sensors (depth & front furrow width) Draught Force

  16. Broadbalk • Winter wheat • (continuous & rotation) • Started 1843

  17. Specific draught measurements; Broadbalk Experiment, Rothamsted Watts, Clark, Poulton, Powlson, Whitmore. Soil Use and Management22,334-341 (2006)

  18. Broadbalk – SOC and specific draught Watts, Clark, Poulton, Powlson, Whitmore. Soil Use and Management 22,334-341 (2006)

  19. “Labile C” – easily oxidisable – about 10% of total C (microbial biomass + metabolites) • Increased by straw incorporation and N fertilizer application (larger yields, larger residue returns) • “Labile C” – correlated with: • Increased aggregate stability • Increased water infiltration rate Blair, Faulkner, Till, Poulton. Soil & Tillage Research91, 30-38 (2006)

  20. Rothamsted, Broadbalk Experiment Labile C Total C Water infiltration rate related to “labile C” – increased by straw and N fertilizer Blair, Faulkner, Till, Poulton. Soil & Tillage Research91, 30-38 (2006)

  21. Rothamsted, Broadbalk Experiment Labile C Total C Aggregate stability related to “labile C” – increased by straw and N fertilizer Blair, Faulkner, Till, Poulton. Soil & Tillage Research91, 30-38 (2006)

  22. ESRC transdisciplinary seminar, 20th April 2004 The benefits of SOM may not be directly proportional to total SOC content Arable 45t C ha-1 Bare fallow 40t C ha-1 Managed grass 80t C ha-1

  23. Concluding comments • Maintaining SOC content is vital for soil functioning (“soil quality”) • So unwise to regularly remove crop residues – one of few ways to add OM • But considerable OM inputs from roots, stubble, chaff – these continue even if straw removed • A suggestion – only remove straw every 2nd or 3rd year

  24. Concluding comments • Maintaining SOC is essential for soil functioning (“soil quality”) • Crop production • Run-off, erosion • So unwise to regularly remove crop residues – one of few ways to add OM to soil • But considerable OM inputs from roots, stubble, chaff – these continue even if straw is removed • A suggestion: only remove straw every 2nd or 3rd year • Region specific modelling can provide guidance • Implications for straw availability for biofuel • But care – small SOC changes may have disproportionately large impacts on soil (physical) properties

  25. Sanguesa, Spain 200 GWhr/yr Uses 160,000 t cereal straw per year Electricity for 50,000 homes

  26. Putting a value on SOM

More Related