Effect of organic farming on soil erosion and soil structure of reclaimed Tepetates in Tlaxcala, Mexico [Elektronische Ressource] / eingereicht von Mathieu Haulon
124 Pages
English
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Effect of organic farming on soil erosion and soil structure of reclaimed Tepetates in Tlaxcala, Mexico [Elektronische Ressource] / eingereicht von Mathieu Haulon

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124 Pages
English

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Aus dem Institut für Bodenkunde und Bodenerhaltungder Justus-Liebig-Universität GießenProf. Dr. Peter Felix-HenningsenEffect of organic farming on soil erosion and soil structureof reclaimed Tepetates in Tlaxcala, MexicoDissertation zur Erlangung des Doktorgrades der Agrarwissenschaftenam Fachbereich 09- Agrarwissenschaften, Ökotrophologie und Umweltmanagement -der Justus-Liebig-Universität Gießeneingereicht von Mathieu Haulonaus Brüssel/BelgienGießen 2008This thesis was accepted as an Inaugural Dissertation by the Justus-Liebig-UniversityGiesssen, Fachbereich 09 “Agrarwissenschaften, Ökotrophologie und Umweltmanagement”Index iIndexIndex_____________________________________________________________________ iZusammenfassung__________________________________________________________vAbstract _________________________________________________________________ viList of Figures ___________________________________________________________ viiList of tables______________________________________________________________ ixList of abbreviations ______________________________________________________ xii1. Introduction ___________________________________________________________11.1. Tepetates and erosion________________________________________________11.1.1. Tepetates: hardened volcanic horizons with agriculture potential _______________________ 11.1.1.1. Definition ________________________________________________________________ 11.1.1.2.

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Aus dem Institut für Bodenkunde und Bodenerhaltung
der Justus-Liebig-Universität Gießen
Prof. Dr. Peter Felix-Henningsen
Effect of organic farming on soil erosion and soil structure
of reclaimed Tepetates in Tlaxcala, Mexico
Dissertation zur Erlangung des Doktorgrades der Agrarwissenschaften
am Fachbereich 09
- Agrarwissenschaften, Ökotrophologie und Umweltmanagement -
der Justus-Liebig-Universität Gießen
eingereicht von Mathieu Haulon
aus Brüssel/Belgien
Gießen 2008This thesis was accepted as an Inaugural Dissertation by the Justus-Liebig-University
Giesssen, Fachbereich 09 “Agrarwissenschaften, Ökotrophologie und Umweltmanagement”Index i
Index
Index_____________________________________________________________________ i
Zusammenfassung__________________________________________________________v
Abstract _________________________________________________________________ vi
List of Figures ___________________________________________________________ vii
List of tables______________________________________________________________ ix
List of abbreviations ______________________________________________________ xii
1. Introduction ___________________________________________________________1
1.1. Tepetates and erosion________________________________________________1
1.1.1. Tepetates: hardened volcanic horizons with agriculture potential _______________________ 1
1.1.1.1. Definition ________________________________________________________________ 1
1.1.1.2. Distribution ______________________________________________________________ 1
1.1.1.3. Origin, hardening and conditions of formation ___________________________________ 2
1.1.1.4. Emergence due to erosion ___________________________________________________ 4
1.1.1.5. Properties ________________________________________________________________ 5
1.1.1.6. Tepetate rehabilitation ______________________________________________________ 6
1.1.2. Structure, erosion and organic farming ___________________________________________ 9
1.2. Objectives ________________________________________________________12
2. Tlaxcala: a state affected by tepetates _____________________________________13
2.1. Physiographic overview _____________________________________________13
2.2. Climate __________________________________________________________13
2.3. Geology __________________________________________________________14
2.4. Soils _____________________________________________________________15
2.5. Soil use and agriculture _____________________________________________16
2.5.1. Agriculture ________________________________________________________________ 16
2.5.2. Forest ____________________________________________________________________ 16
2.6. Sociodemographic context___________________________________________16
2.6.1. Economy and employment ____________________________________________________ 17
2.6.2. Migration _________________________________________________________________ 18
2.6.3. Farm unit structure __________________________________________________________ 18
3. Materials and methods _________________________________________________19Index ii
3.1. Tlalpan experimental site ___________________________________________19
3.2. Managements _____________________________________________________19
3.3. Crops and fertilization______________________________________________20
3.4. Methods__________________________________________________________21
3.4.1. Soil loss and runoff__________________________________________________________ 21
3.4.2. Rain erosivity ______________________________________________________________ 23
3.4.3. Vegetation cover____________________________________________________________ 24
3.4.4. Aggregate stability __________________________________________________________ 24
3.4.4.1. Percolation stability _______________________________________________________ 24
3.4.4.2. Aggregate size distribution _________________________________________________ 25
3.4.4.3. Sampling _______________________________________________________________ 26
3.4.4.4. Statistical analysis ________________________________________________________ 26
3.4.5. Particle size distribution ______________________________________________________ 26
3.4.6. Porosity and pore size distribution ______________________________________________ 27
3.4.7. Soil Organic Carbon_________________________________________________________ 27
4. Results_______________________________________________________________28
4.1. Erosivity and soil erosion____________________________________________28
4.1.1. Rainfall erosivity ___________________________________________________________ 28
4.1.1.1. Annual precipitation_______________________________________________________ 28
4.1.1.2. Monthly precipitation______________________________________________________ 29
4.1.1.3. Rainfall patterns in Tlalpan _________________________________________________ 30
4.1.2. Runoff and soil loss _________________________________________________________ 31
4.1.3. Vegetation cover____________________________________________________________ 32
4.1.3.1. 2002 ___________________________________________________________________ 33
4.1.3.2. 2003 ___________________________________________________________________ 33
4.1.3.3. 2004 ___________________________________________________________________ 35
4.1.3.4. 2005 ___________________________________________________________________ 35
4.2. Soil properties and crop production___________________________________36
4.2.1. Soil Organic Carbon_________________________________________________________ 36
4.2.2. Soil water content___________________________________________________________ 38
4.2.3. Crop production ____________________________________________________________ 39
4.3. Soil structure______________________________________________________39
4.3.1. Particle size distribution ______________________________________________________ 39
4.3.2. Aggregation _______________________________________________________________ 42
4.3.2.1. Dry aggregate size distribution ______________________________________________ 42
4.3.2.2. Aggregate stability ________________________________________________________ 44
4.3.3. Porosity and pore size distribution ______________________________________________ 48Index iii
4.3.3.1. Total porosity and bulk density ______________________________________________ 48
4.3.3.2. Pore size distribution ______________________________________________________ 49
4.3.3.3. Effect of depth on porosity__________________________________________________ 50
4.3.3.4. Effect of ridge and furrow systems on porosity __________________________________ 51
4.4. Statistical analysis _________________________________________________52
4.4.1. Relationship between SOC, aggregate stability and erodibility ________________________ 52
4.4.2. Soil loss and runoff prediction _________________________________________________ 53
4.4.2.1. About the data set_________________________________________________________ 53
4.4.2.2. About the variables _______________________________________________________ 54
4.4.2.3. Relationship between erosivity and erosion_____________________________________ 55
4.4.2.4. Soil loss and runoff prediction _______________________________________________ 55
5. Discussion: Effect of organic farming on soil erosion and soil structure _________59
5.1. Erosivity _________________________________________________________59
5.2. Effect of organic farming on soil erosion _______________________________59
5.2.1. Carbon dynamic in reclaimed tepetates __________________________________________ 59
5.2.1.1. Incorporation and accumulation of SOC _______________________________________ 59
5.2.1.2. Carbon losses ____________________________________________________________ 61
5.2.2. Vegetation cover____________________________________________________________ 63
5.2.2.1. Crop development and vegetation cover _______________________________________ 63
5.2.2.2. Crop association__________________________________________________________ 65
5.2.2.3. Mulching _______________________________________________________________ 66
5.2.3. Runoff and erosion rates in reclaimed tepetates____________________________________ 66
5.2.4. Evolution of erosion rates_____________________________________________________ 68
5.3. Effect of organic management on soil structure _________________________70
5.3.1. Aggregate stability dynamic and organic management ______________________________ 70
5.3.2. Porosity and infiltration ______________________________________________________ 73
5.3.2.1. Presence and effect of fragments on porosity in recently reclaimed tepetates. __________ 73
5.3.2.2. Effect of management on soil porosity ________________________________________ 74
5.3.3. About tillage and residue management___________________________________________ 75
6. Conclusion ___________________________________________________________77
Summary ________________________________________________________________80
References _______________________________________________________________82
Acknowledgements ________________________________________________________93
Appendix 1. Rain erosivity________________________________________________95
Appendix 2. Soil loss and runoff ___________________________________________97
Appendix 3. Vegetation cover _____________________________________________99Index iv
Appendix 4. Soil properties and crop production ____________________________100
Appendix 5. Soil loss and runoff prediction _________________________________103
Appendix 6. Aggregation ________________________________________________105
Appendix 7. Porosity____________________________________________________107Zusammenfassung v
Zusammenfassung
In den Hochländern Mexicos werden Landschaften, in denen durch Kieselsäure verhärtete,
sterile Schichten (Tepetates) als Folge von Bodenerosion frei gelegt wurden, rekultiviert, um
neue landwirtschaftliche Nutzflächen zu gewinnen. Um die Nachhaltigkeit der
Rekultivierungsmaßnahmen zu verbessern, wurde der Einfluss der organischen
Landwirtschaft auf das Bodengefüge und die Bodenerosion von rekultivierten
Tepetateflächen im Feldmaßstab unter natürlichen Bedingungen untersucht. Organische
Festsubstanz (SOC) stellt den bedeutendsten Faktor dar, der die jährlichen Erosionsraten der
rekultivierten Tepetateflächen kontrolliert. Neben einer kurzfristig zunehmenden
Gefügestabilität führt die organische Düngung zu einer dichteren Vegetationsdecke, was
wiederum die Bodenerosion im Mittel von 3 Jahren nach der Krustenfragmentierung auf 9,9
-1 -1t ha-1a-1 reduziert, im Vergleich zu 14,6 t ha a bei Mineraldüngung. In 16 Jahren seit der
Rekultivierung unter konventioneller Landbewirtschaftung sanken die Erosionsraten auf 1,1
-1 -1bis 5,6 t ha a ab. Die Etablierung der organischen Landwirtschaft steigerte zwar den
Gehalt an organischer Substanz der Böden, hatte im Vergleich zu anderen
Bewirtschaftungsweisen jedoch keinen nachweisbaren Effekt auf die Bodenerosion. In
stärkerem Maße als die organische Landwirtschaft per se, garantieren die regelmäßige
Einarbeitung von organischem Material und eine dichte Vegetationsdecke eine
Erosionskontrolle und nachhaltige Rekultivierung der Tepetateflächen.Abstract vi
Abstract
In Mexican highlands, vast areas are covered by hardened and sterile volcanic layers
(tepetates) that showed up to the surface after erosion of the overlying soil. The rehabilitation
of tepetates is a way to increase arable land and combat desertification. In order to develop
sustainable rehabilitation strategies, the effect of organic farming on soil erosion and soil
structure in reclaimed tepetates was investigated at field scale and under natural condition. In
addition to short term structural improvement, organic farming provided higher vegetation
cover and increased carbon accumulation rates, resulting in a decrease of soil erosion to 9.9 t
-1 -1 -1 -1ha yr on average over a period of 3 years after fragmentation compared to 14.6 t ha yr
with conventional management (mineral fertilization). In reclaimed tepetates cultivated for
-1 -1more than 16 years, erosion rates ranged between 1.1 and 5.6 t ha yr . SOC was the main
parameter controlling annual erosion rates and their evolution over time in reclaimed tepetates.
More than organic farming per se, it is the regular incorporation of organic material and the
development of high vegetation cover which will guarantee erosion control and sustainable
rehabilitation of tepetatesList of figures vii
List of Figures
Figure 1: Expected evolution of fertility, runoff and erosion during the rehabilitation
process under two extreme scenarios........................................................................8
Figure 2: Ombrothermic diagram of Hueyotlipan meteorological station. 1961-1998 ...........14
Figure 3: Demographic growth and distribution between rural and urban population in
the State of Tlaxcala from 1910 to 2005. Sources: INEGI, censos de
población y vivienda 1930 to 2000 and Conteos de Población y Vivienda
1995 and 2005.........................................................................................................17
Figure 4: Map of Tlalpan experimental site and main characteristics of the plots..................19
Figure 5: Average monthly precipitation and standard deviation at Tlalpan based on
records from 1991 to 1997 and from 2002 to 2005. ...............................................29
Figure 6: Start time of rainfall events (> 1mm) between 2002 and 2005 in Tlalpan...............30
Figure 7: Annual soil loss, runoff, runoff coefficient and sediment discharge in Tlalpan
from 2003 to 2005. See Table A- 2 for details. ......................................................31
Figure 8: Composition of vegetation cover in 2003 in Tlalpan...............................................34
Figure 9: Distribution of vegetation cover (average value), precipitation and soil loss
(average value) during 2003 in Tlalpan..................................................................34
Figure 10: Distribution of vegetation cover (predicted average value of all plots),
precipitation and soil loss (average value of all plots) during 2004 in Tlalpan......35
Figure 11: Distribution of vegetation cover (average value of all plots), precipitation
and soil loss (average value of all plots) during 2005 in Tlalpan ...........................36
Figure 12: Monitoring of soil water content (gravimetric) at 10 cm depth by TDR
during 2004 cropping season. Cf Table A- 8..........................................................38
Figure 13: Monitoring of soil water content (gravimetric) by tensiometers during 2005
cropping season (weighted average from measures done at 5, 10, 15, 25 and
40 cm depth). Cf Table A- 9. ..................................................................................39
Figure 14: Particle size distribution in Tlalpan in plots were erosion was measured..............40
Figure 15: Dry aggregate size distribution during the rainfall season in 2005 in Tlalpan.......43
Figure 16: Linear regression between MWD and <0.59 mm fraction in 2004........................44
Figure 17: Effect of management and age of rehabilitation on mean PSw over the
period 2003-2005. Different letter indicate significant difference (p<0.05). .........45
Figure 18: Aggregate stability (PSw) in 2005 and its evolution during the crop cycle...........46
-1Figure 19: PS (ml 10 min ) values in 02-C and 02-O during the cropping season in
2005 in relation to aggregate size. ..........................................................................46
Figure 20: Pore size distribution in 2003, 2004 and 2005 .......................................................50
Figure 21: effect of depth on pore size distribution in 2005 in Tlalpan ..................................51List of figures viii
Figure 22: Pore size distribution at 5 cm depth in ridge and furrow maize cropping in
reclaimed tepetate (Table A- 22). ...........................................................................51
Figure 23: relationship between SOC and annual runoff rates in plots reclaimed in 1986
and 2002..................................................................................................................57
Figure 24: Cause-effect relationship between water supply, vegetation cover and soil
erosion. + and – indicate an increasing (+) and decreasing (-) effect.....................65