71st SWCS International Annual Conference July 24-27, 2016 Louisville, KY

1. The effects of tillage, cover crops,
and residue removal on soil organic
carbon
JENNIFER TURNER USDA, NRCS
KENNETH R OLSON UIUC, ACES, NRES
JULY 26, 2016
SWCS INTERNATIONAL ANNUAL CONFERENCE

2. Background
In 2014, a senior collaborative research team from Illinois, Iowa, Ohio,
and Wisconsin conducted a meta-analysis of more than 120 studies on
soil organic carbon and found many of the studies may have had
significant flaws.
Olson et al., 2014

3. Background
Use baseline SOC measurement at beginning of the study
◦ -Many studies use treatment compared to MP
◦ -Possibly over estimating how much SOC is retained
Depth needs to be sampled all the way to the root zone
◦ -Many studies sample to 30 cm or less
◦ -Distribution is different in the tillage treatments

4. Research Objectives
Use pretreatment SOC stock to compare to end of study SOC stock
1) Cover crop treatment
2) Residue removal treatment
3) Tillage treatment

5. Factors that determine amount of
SOC
Environmental:
Rainfall, temperature, soil type, amount of soil erosion
Human:
Tillage, type of vegetation grown, amount of fertilizer applied

6. Why do we care about SOC?
58% of organic matter is SOC
Every 1% of organic matter can hold a ½ acre inch of water- important in
growing crops
Humus has many negative charges which helps keep positively charge
ions from leaching- such as calcium, potassium and magnesium
‐SARE, 2009

7. Why do we care about SOC?
More food sources for microbes that provide important benefits for soil such as
better aggregate stability, better root growth and releasing the nutrients for the
growing plants to utilize
Organic matter helps hold pesticides from leaching so microbes have time to
break it down.
‐SARE, 2009

8. Research Location

9. Research Design

10. NT Cover Crop Treatment effect on SOC

11. CP Cover Crop Treatment effect on SOC

12. MP Cover Crop Treatment effect on SOC

13. Cover Crop Results
All treatments retained more SOC in 2013 versus 2009
Treatments with cover crops retained more SOC than the no cover crop
treatment
NT with the cover crop treatment retained the most SOC
at a little over 60 Mt C/ha/yr

14. NT Residue Removal Treatment effect on SOC

15. CP Residue Removal Treatment effect on SOC

16. MP Residue Removal Treatment effect on SOC

17. Residue Treatment Results
All treatments retained more SOC in 2013 versus 2009
The NT and CP treatments where residue was retained had higher SOC
than where residue was removed. But MP treatment where residue was
removed had higher SOC.
The difference between 2009 and 2013 was not as large as the cover
crop treatment results

18. Tillage Treatment effect on SOC

19. Tillage Treatment Results

20. Tillage Treatment Results
All treatments retained more SOC in 2013 versus 2009
NT retained more SOC than the other two tillages
The distribution of SOC by depth was different in MP than the other two
tillage treatments

21. Yield Results

22. Beyond the Research
Raise awareness about the importance of no-till and cover crops to
increase the amount of organic carbon in their crop fields.
Advise about need to keep soil productive by building the amount of soil
organic carbon in their soil.
Mitigation for climate change which could include carbon credits to
landowners willing to build soil organic carbon.

23. References
Olson, K.R., M.M. Al-Kaisi, R. Lal, B. Lowery, 2014. Experimental
consideration, treatments, and methods in determining soil organic
sequestration. Soil Science Society of America Journal. 78:348-360.
Sustainable Agriculture Research and Education (SARE). 2012.
Managing Cover Crops Profitably, Third Edition. United Book Press, Inc.
June 2012.

24. Questions?
jennifer.turner@ia.usda.gov
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