1. ORGANIC CARBON SEQUESTRATION EFFICIENCY
OF SUSTAINABLE MANAGEMENT PRACTICES
UNDER ORGANIC RAINFED MEDITERRANEAN CROPS
• Martínez-Mena, M.
• de Vente, J.
• Boix-Fayos, C.
• Garcia-Franco, N.
• Almagro, M.
CEBAS-CSIC
• Melgares de Aguilar, J.
• Gonzalez, D.

2. Introduction Objectives
SUSTAINABLE
MANAGEMENT
PRACTICES
No Tillage (NT)
Reduced Tillage (RT)
Green Manure (RTG)
Soil
physical
properties
Soil C
cycle
↓ Soil loss
by erosion
Yield
Productivity
Runoff control
& ↑ SWC
↑ C inputs

3. Experimentaldesign Study areas
NT
RTG
RT

4. Cehegín Zarzadilla
Soil property Almond tree Almond tree Cereal
Clay (%) 15.5 4. 2 17.76 3.7 30.65 3.9
Silt (%) 41.5 9.0 48.9 11.5 59.6 2.8
Sand (%) 43.0 12.0 33.2 14.8 9.6 5.9
SOC (%) 1.2 0.3 2.30 0.6 0.74 3.9
Total N (%) 0.12 0.04 0.20 0.04 0.07 0.01
Polsen (ppm) 15.60 5.8 41.8 18.7 6.1 1.8
CaCO3 (%) 54. 2 11.5 44 9.2 56 10.1
pH (water, 1:25) 8.7 0.2 8.8 0.14 9.14 0.17
EC (siems cm-1) 168.3 23.3 90.8 14.7 73.3 5.9
General soil characteristics of the study areas

5. Experimentaldesign Cereal management practices
Conventional tillage
Labours/year : 4/5
Depth: 40 cm
Reduced contour tillage
Labours/year : 2
Depth: 20 cm

6. Experimentaldesign Almond tree management practices
Conventional tillage
Labours/year : 4/5
Depth: 20 cm
No tillage
Reduced tillage +
green manure
Labours/year : 2
Depth: 15/20 cm
Reduced tillage
Labours/year : 2
Depth: 15/20 cm

7. ZarzadilladeTotanaCehegin Green manure2009 (P=345 mm)
Vicia sativa + Avena sativa: 3:1 at 150 kg ha-1
Vicia sativa + barley: at 150 kg ha-1 3:1
2011 (P=230 mm)

8. Experimentaldesign Erosion plots

9. Results
Soil water storage capacity
Nov-08
Dec-08
Jan-09
Feb-09
Mar-09
Apr-09
May-09
Jun-09
Jul-09
Aug-09
Sept-09
Oct-09
Nov-09
Dec-09
Jan-10
Feb-10
Mar-10
Apr-10
May-10
Jun-10
Jul-10
Aug-10
Sep-10
Oct-10
Nov-10
Dec-10
Jan-11
Feb-11
Mar-11
Apr-11
May-11
Jun-11
Jul-11
Aug-11
Sep-11
oCT-11
Nov-11
Dec-11
Jan-12
Feb-12
Mar-12
Apr-12
May-12
Jun-12
Jul-12
Aug-12
Sep-12
oCT-12
Precipitation(mm)
0
20
40
60
80
100
120
140
Soilwatercontent(%)
0
5
10
15
20
25
30RT
RTG
NT
2009 2010 2011 2012
Cehegin almond trees
349.5 mm 439.8 mm 230.9 mm 451.0 mmTotal rainfall:

10. Results Soil water storage capacity
0,0
5,0
10,0
15,0
20,0
25,0
30,0
19/02/2009
19/04/2009
19/06/2009
19/08/2009
19/10/2009
19/12/2009
19/02/2010
19/04/2010
19/06/2010
19/08/2010
19/10/2010
19/12/2010
19/02/2011
19/04/2011
19/06/2011
19/08/2011
19/10/2011
19/12/2011
19/02/2012
19/04/2012
19/06/2012
19/08/2012
19/10/2012
date
soilwatercontent(%)
CT RT RTG
Zarzadilla almond trees
Runoff (mm) from 14 events (period 2011-2012)
Almond Cereal
CT RT RTG CT RT
4.30 1.83 1.68 4.1 2.82

11. Almond Cereal
CT RT RTG CT RT
g m-2
Soil
loss
14.90 5.43 9.03 59.36 24.26
Dates from 14 events ocured in Zarzadilla (2011-2012)
OC 0.43 0.20 0.27 0.56 0.26
g m-2
N 0.034 0.016 0.024 0.037 0.025
P 0.068 0.028 0.030 0.024 0.039
g Kg-1
OC 26.87 38.31 27.79 10.18 14.02
N 2.65 3.53 3.0 0.93 1.34
mg Kg-1 P* 60.74 89.31 56.26 10.25 30.27
erosion and nutrient mobilizationResults

12. OC, N and P enrichment in sedimentResults
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
OC N P
Ratiosediment/soil
Conventional tillage Reduced tillage
cereal
0
0,5
1
1,5
2
2,5
3
OC N P
Ratiosediment/soil
Conventional tillage Reduced tillage Reduced Tillage + Green manure
Almond trees

13. Potential for carbon sequestration
Soil aggregates size distributionResults
0
10
20
30
40
50
60
> 2 2-0.25 0.25-0.053 <0.053
Particle size (mm)
percentage
Conventional tillage Reduced tillage Reduced tillage +Green manure No tillage
MWD
CT 0.7 0.08
RT 0.89 0.02
RTG 1.06 0.05
NT 1.05 0.05

14. 0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
>2 2-0.25 0.25-0.05
Aggregate size (mm)
OC(g/Kg)
CT RT RTG NT
0
0,5
1
1,5
2
2,5
3
RT RTG NT
Treatments
OC(g/Kg)
microaggregates within macroaggregates microaggregates within mesoaggregates
OC distribution within soil aggregates at surfaceResults

15. 0
0,5
1
1,5
2
2,5
3
3,5
>2 2-0.25 0.25-0.05
Aggregate size (mm)
OC(g/kg)
CT RT RTG NT
0
0,5
1
1,5
2
2,5
RT RTG NT
Treatments
OC(g/Kg)
microaggregates within macroaggregates microaggregates within mesoaggregates
OC less vulnerable to change in enviromental factors
OC distribution within soil aggregates at depthResults

16. 3rd May 2012
7th June 2012
5th July 2012
5th Sep 2012
10th Oct 2012
12th Nov 2012
Pre-tillage on 3rd Dec2012
Post-tillage on 3rd Dec 2012
Post-tillage on 4th Dec 2012
Post-tillage on 5th Dec 2012
Post-tillage on 7th Dec 2012
Jan 2013
Feb 2013
Mar 2013
SoilrespirationingCm
-2
day
-1
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
a
ab
b
a
b b
ab
a
a
b
b
cb
a
a
Reduced Tillage + Green Manure (RTG)
No Tillage (NT)
Reduced Tillage (RT)
bb
Soil respirationResults

17. SOC stock (g m-2)
Conventional tillage 500.0 ± 35.4
Reduced tillage 660.5 ± 64.39
Reduced tillage + green manure 770.1 ± 81.95
No tillage 596.3 ± 49.79
SOC stockResults
+ 17%
+ 35%
+ 16%

18. Green manure balanceResults

19. Almond crop yield
Year
2010 2012
Cropyield(Kgtree
-1
)
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
CT
RT
RTG
CT RT RTG
0,00
0,05
0,10
0,15
0,20
0,25
Zarzadilla Cehegin
Year
2009 2010 2011 2012
Kgtree
-1
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
RT
RTG
NT
Results

20. Erosion control OC outputs OC Stock Crop productivity
Runoff Sediments Erosion Soil
Respiration
Soil Aggregates Yield crop Percentage
of kernel
RT        
RTG        
NT     
Sustainable management practices in organic rainfed crops:
comparison with conventional practices.Conclusions
Cover crops can provide considerable environmental benefits in almonds, and that any
competition for water between almond tree and cover crops can be offset by the
improvements of the above mentioned soil conditions, which would ultimately benefit the
almonds themselves.
Some tillage is required to maintain optimal crop production in rainfed almonds trees
in semiarid agroecosystems