1. Organic Management Systems to Enhance Ecosystem Services
Michel Cavigelli, Steven Mirsky,
John Doran
Sustainable Agricultural Systems Lab
Beltsville Agricultural Research Center, Maryland
and Renewing Earth And its People (REAP)
Presented at ASA-CSSA-SSSA Annual Meetings, San Antonio, Texas, 1

2. Organic Farming Managing ecological processes to provide
ecosystem services
Provisioning: food production
Regulating: water quality, climate, pest populations
Supporting: soil retention, nutrient cycling
Cultural: healthy livelihood, aesthetic experience
No synthetic fertilizers
No synthetic pesticides
No GMOs
One definition of organic agriculture that is very comprehensive is from IFOAM 2

3. Organic Farming Crop rotations Cover crops Animal manures Tillage
One definition of organic agriculture that is very comprehensive is from IFOAM 3

4. Ecosystem Services Organic Farming and SOM
Means for 9 LTARs
Organic agriculture provides a number of ecosystem services, including increasing SOM. These data from Marriott and Wander show that SOM is greater in organic cropping systems compared to conventional systems regardless of whether the organic systems rely on animal manures or legumes alone for soil fertility. These data are means from 9 LTARs in the USA.
As with many comparisons between organic and conventional farming, however, conventional refers to systems that include mineral fertilizers and synthetic pesticides, AND Conv. Tillage. Few examples comparing organic with NT because there are few LTARs that include both NT and Organic.
Marriott and Wander, 2006 4

5. Organic Farming and SOM
Soil organic carbon
(Mg C ha-1)
Study
Location
Sampling depth (cm) CT
Org NT
Robertson et al. 2000*
KBS, MI
7.5
9.4
10.2
12.4
Cavigelli et al. unpub’d**
FSP, MD
100
51.7 b
60.8 a
54.9 b
The two LTARs that compare organic and NT systems show a similar pattern as just illustrated in that soil C is greater in organic than conventional systems. However, when NT is included in the comparison, SOC is greater in NT than Org, at least in surface cm of sandy soils when no animal manures are added.
When animal manures are added and when SOC is measured to 1 m depth on a silt loam, SOC is greater in Org than NT.
*sandy loam, no manure addition
**silt loam, manure added to Org 5

6. Cavigelli, unpublished
0-2.5 cm
2.5-5 cm
5-10 cm
10-25 cm
25-50 cm
When we look at how that SOC is distributed with depth in the latter study we see a classic pattern between the NT and CT soils in that in surface 5 cm, SOC is greater in NT than CT but below that depth there are few, if any differences in SOC.
By contrast, SOC level is intermediate in the surface 5 cm for the Organic system but greater than for CT and NT at 5-10 and cm depths.
Since the amount of tillage in these organic systems is substantial, we know that these C levels can be sustained despite substantial tillage. cm
Cavigelli, unpublished 6

7. SOM Provides Supporting and Regulating Ecosystem Services
Increases Soil Fertility
Reduces Global Warming
Potential (Soil C Sequestration)
Stabilizes Soil to Resist Erosion
Increasing SOM, of course, provides a number of benefits to soils and the environment. 7

8. Organic Farming and Nitrogen Fertility (FSP, Maryland)
Animal manures
Organic farming often increases soil N fertility as shown in this figure comparing particulate organic matter nitrogen (POM-N) among a conventional and organic cropping systems. In this case, POM-N is similar in CT and NT systems and greater in organic systems, especially as the rotation length of the organic systems increases. The 2, 3, and 6 behind Org refer to the number of years in a crop rotation.
However, a concern among organic farmers, especially in the Chesapeake Bay watershed where Steven Mirsky and I work, is that if this inherent soil fertility is increased by repetitive applications of animal manures, soil P levels may approach or reach unsustainable levels.
Spargo et al. 2011 8

9. Organic Farming and Global Warming Potential
CO2 eqvt
(kg CO2eqvt ha-1 yr-1)
System
Soil C*
N2O
Energy
GWP*
Chisel Till
1080 a
406 ab
862
2348 a
No-Till
0 b
303 b
807
1110 b
Organic
-1953 c
737 a
344**
-872 c**
* Negative value indicates mitigation of global warming
** Strongly dependent on manure transportation distance
Cavigelli et al., 2009 9

10. Organic Farming and Soil Erosion
*WEPP=Water Erosion Prediction Project. All systems are corn- soybean-wheat/legume rotations on Mattapeake soil in Maryland, 5% slope, 60 m slope length; 100 year simulation.
Green et al. 2005
Mg ha-1 yr-1
A similar result was seen in a simulation of soil loss in the long-term Farming Systems Project in Beltsville, Maryland. In this case, there was greater tillage in the organic than in a conventional system.
However, when compared with NT, predicted soil loss was greater in organic than NT. 10

11. Provisioning Services: Organic Farming and Food Production
On average, grain yields are lower in organic than conventional systems in developed countries (Badgley et al. 2007).
85%* % %
*Calculated from Badgley et al using only results from side by side comparisons. 11

12. Organic Farming and Ecosystem Services
Supporting and Regulating Services
Increased SOM
Improves soil fertility (but P concerns)
Decreases GWP
Does not necessarily reduce soil
erosion (few data)
Provisioning Services
Grain yields decrease
Cultural Services
Labor intensive
Organic premiums 12

13. Can We Improve Ecosystem Services
Provided by Organic Cropping Systems?
Increase crop phenological diversity
Improve manure management
Sidedressing
Injection
Integrating with legume covers
Reduce tillage
Intensity
Frequency
Comparisons between organic and conventional systems provide some insights on ecosystem services provided by organic systems but not on how to improve organic systems. 13

14. Increasing crop phenological diversity improves corn yieldsb
*years with normal rainfall
Cavigelli et al, 2008
Increasing crop phenological diversity can increase grain yields in organic systems. This example is from Maryland, showing that
C-r-S-W/S
C-r-S-v
C-r-S-W-v
C-r-S-W-A-A-A 14

15. (6 year mean, weedy and weed-free microplots)
Weed Cover
(6 year mean)
Corn Yield Loss to
Weed Competition
(6 year mean, weedy and weed-free microplots)
Teasdale and Cavigelli, 2010

16. Increasing crop phenological diversity reduces economic risk
SD+74
+56
+40
+203
+381
Net Returns
Cavigelli et al., 2009

17. Frequency of manure application
Increasing crop phenological diversity improves soil fertility while limiting animal manure applications
System
Potentially
mineralizable N
Frequency of manure application CT
229 b NA NT
241 b
Org2
297 a
1 of 2 yrs
Org3
323 a
2 of 3 years
Org6
325 a
2 of 6 years
Increasing crop phenological diversity by including a perennial legume crop provides the same N fertility benefit as annual legume cover crops but with significantly reduced frequency of animal manure application, thus reducing P application.
Spargo et al., 2011 17

18. Increasing crop phenological diversity reduces soil N2O emissions while maintaining soil C levels
While potentially mineralizable N seems to be similar among organic cropping systems, the longer, more diverse crop rotation seems to have additional conservation benefits, including reducing soil N2O emissions. This is in part due to lower N2O emissions during the portions of the rotation that had low N demanding crops.
Cavigelli et al. Unpublished 18

19. Increasing crop phenological diversity reduces predicted soil loss by erosion (RUSLE2*)
Increasing crop phenological diversity can reduce soil loss by erosion
* RUSLE2 is a hybrid empirical—process-based model. K Factor = 0.28, western MD, 2-5% slope; results similar with other settings
Pilkowski and Cavigelli, Unpublished 19

20. Improving Manure Management
Applying OMRI amendments pre-plant vs. sidedress following a vetch cover crop
Spargo et al. Unpublished

21. Reducing Tillage Cover crop-based organic rotational no-till grain production
For weed control in absence of herbicides and tillage….
Use cover crops
Fall planted
Legume-corn
Grass-soybean
Produce weed-suppressive mulch
Mechanically terminated in spring
Mirsky et al. 2012

22. (adapted from South America, popularized by Rodale)
Roller/Crimper
(adapted from South America, popularized by Rodale)
Effective at terminating many winter annual cover crops when flowering
Crimping bars
Produces unidirectional mulch
Front-mounted 22

23. Supplemental weed control
Minimal disturbance, high-residue cultivator
Between-row cultivation
Thin vertical shanks and flat, wide sweeps
Does not invert the soil
Does not drag residues
Especially important when weed seedbanks are high or with perennial weeds

24. Tillage regimes based on management (3 year rotation)
Year 1 Year 2 Year 3
=5+
= 3 +
= 3 +
= 3 +
= 3 +
= 3 +
= 5 +
Traditional organic
Hairy vetch
Corn
Cereal rye
Soybean
Wheat
X = 25
Fix spacing
= 2 +
= 2 +
= 3 +
= 3 +
= 3 +
Cover crop-based organic rotational
no-till
Hairy vetch
Corn
Cereal rye
Soybean
Wheat
X = 13

25. Corn and Soybean Yields
(Results from 2-4 site years per location)
Corn
yield SD
County
average
kg ha
BARC (MD)
7448
3068
8093
PSU (PA)
4646
1941
8532
Rodale (PA)
6255
3059
8720
Soybean
yield SD
County
average
kg ha
BARC (MD)
2555
1013
2084
PSU (PA)
2359
609
2756
Rodale (PA)
2752
856
3563
Remove improved yield, just report sites, number of site years, and yield and variability is based on additional supplementary management low rainfall.
Better silage
Mirsky et al. 2012 25

26. Challenges with organic rotational no-till corn production
Limited corn growing season (Mischler et al. 2010)
Crop establishment (Mirsky et al. 2012)
Pests
Planting equipment performance
Inadequate nitrogen from vetch (Mischler et al. 2010)
Hairy vetch has inconsistent weed control efficacy
Less biomass than rye
Fast decomposition (Ruffo and Bollero )

27. Improving the organic rotational no-till corn system
Vetch-rye cover crop mix
Subsurface banding poultry litter
Cuts through residue, places PL in slit, covers slit
Provides N in synchrony with crop demand
Prevents N losses by volatilization (Kleinman 2009)
N Delivered below zone of mulch decomposition
Initiated by USDA-ARS, Auburn, AL

28. Conclusions
Longer, more complex crop rotations in organic systems have
Greater corn yields
Less economic risk
Lower weed pressure
Equivalent soil N avail. with lower dependence on manure (and P loading)
Lower GWP?
Reduced soil erosion

29. Conclusions Reducing tillage in organic systems
Reduces soil erosion
Improves soil quality further
Saves fuel, time
Increases management flexibility for weed control
Redistributes labor over cropping season
Inconsistencies in crop performance
Weed management
Insect management
Cover crop integration