A four years experiment was set up in Tlaxcala, Mexico. Erosion and runoff rates were measured in five terraced plots of 580 to 2200 m2 and with 3-4 % slope. Three plots were fragmented in 1986 and two in 2002. Three farming managements were compared: The "conventional", with mineral fertilization and no incorporation of O.M.; the "improved", with mineral fertilization and incorporation of crop residues, and the "organic" with organic fertilization. Soil structure was assessed by total porosity, pore size distribution and aggregate stability.
Annual precipitation ranged between 507 mm in 2005 to 805 mm in 2003, with annual erosivity of 195 N h-1 and 345 N h-1 respectively. In plots reclaimed in 2002, soil loss ranged from 8.6 to 19.1 t ha-1 yr-1 under conventional management and from 5.5 to 14.1 t ha-1 yr-1 under organic farming. In plots reclaimed in 1986 soil loss ranged from 1.1 to 5.6 t ha-1 yr-1 with no significant difference between managements. The incorporation of fresh organic matter in organic farming provided short term increase in aggregates stability, regardless of the age of rehabilitation. However, aggregate stability was not significantly correlated to SOC nor to erosion rates. Multiple regression analysis showed that for annual values, SOC is the main factor controlling erosion rates in reclaimed tepetates, explaining 64 % of soil loss variance and 79 % of runoff variance. The evolution of erosion rates is therefore dependant on carbon accumulation rates.
After fragmentation, organic farming increased carbon sequestration rate to 0.8 Mg C ha-1 yr- 1 compared to 0.22 Mg C ha-1 yr-1 in conventional management. In plots reclaimed in 1986, carbon sequestration ranged from 0.21 Mg C ha-1 yr-1 in conventional management to 0.37 Mg C ha-1 yr-1 in improved management and 0.61 Mg C ha-1 yr-1 in organic management. Erosion rates in terraced reclaimed tepetates could decrease below tolerable value (< 10 t ha-1 yr-1) three years after fragmentation under organic farming, compared to seven years under conventional farming.
Results also confirmed the key role played by vegetation cover (accounting for 27 % of soil loss variance for single events) and emphasize the importance of crop nutrition and crop association to control erosion. Improved management provided
Total porosity ranged from 44.8 % on average in 2003 to 50.4 % on average in 2005. We observed no significant effect of management or age of rehabilitation on soil porosity and pore size distribution, suggesting that high tillage intensity during the cropping season which prevented significant changes in porosity between managements.
This three years study demonstrated that organic farming has a positive effect on soil erosion during rehabilitation of tepetates. However, unless a market for organic products is developed and a certification system established, we recommend organic amendments to be complemented with mineral fertilization to ensure optimum vegetation cover and erosion control.">
 

Giessener Elektronische Bibliothek

GEB - Giessener Elektronische Bibliothek

Hinweis zum Urheberrecht

Bitte beziehen Sie sich beim Zitieren dieses Dokumentes immer auf folgende
URN: urn:nbn:de:hebis:26-opus-69194
URL: http://geb.uni-giessen.de/geb/volltexte/2009/6919/


Effect of organic farming on soil erosion and soil structure of reclaimed Tepetates in Tlaxcala, Mexico

Haulon, Mathieu


pdf-Format: Dokument 1.pdf (1.143 KB)

Bookmark bei Connotea Bookmark bei del.icio.us
Universität Justus-Liebig-Universität Gießen
Institut: Institut für Bodenkunde und Bodenerhaltung
Fachgebiet: Agrarwissenschaften und Umweltmanagement
DDC-Sachgruppe: Landwirtschaft
Dokumentart: Dissertation
Sprache: Englisch
Tag der mündlichen Prüfung: 12.12.2008
Erstellungsjahr: 2008
Publikationsdatum: 30.03.2009
Kurzfassung auf Deutsch: "Tepetates" are hardened layers in the profile of soils from volcanic origin. After erosion of the overlying soil horizon, the tepetates show up on the surface. In the Mexican highlands, along the Trans-Mexican Volcanic Belt, this phenomenon has caused the emergence of vast degraded and sterile areas. The State of Tlaxcala is one of the most affected, with 15 % of the
State area covered by bare tepetates. The rehabilitation of tepetates is a way to increase arable lands and mitigate environmental impact caused by high superficial runoff. Previous research experiences showed that soil erosion control is critical to achieve sustainable tepetates rehabilitation. The application of organic amendments have been repeatedly recommended to increase fertility and soil physical properties after fragmentation, but there is
little data available on the effect of organic farming on soil erosion during the rehabilitation process. The aim of this research is to evaluate the effect of organic farming on soil erosion and soil structure at field scale and under natural conditions.

A four years experiment was set up in Tlaxcala, Mexico. Erosion and runoff rates were measured in five terraced plots of 580 to 2200 m2 and with 3-4 % slope. Three plots were fragmented in 1986 and two in 2002. Three farming managements were compared: The "conventional", with mineral fertilization and no incorporation of O.M.; the "improved", with
mineral fertilization and incorporation of crop residues, and the "organic" with organic fertilization. Soil structure was assessed by total porosity, pore size distribution and aggregate stability.

Annual precipitation ranged between 507 mm in 2005 to 805 mm in 2003, with annual erosivity of 195 N h-1 and 345 N h-1 respectively. In plots reclaimed in 2002, soil loss ranged from 8.6 to 19.1 t ha-1 yr-1 under conventional management and from 5.5 to 14.1 t ha-1 yr-1
under organic farming. In plots reclaimed in 1986 soil loss ranged from 1.1 to 5.6 t ha-1 yr-1
with no significant difference between managements. The incorporation of fresh organic
matter in organic farming provided short term increase in aggregates stability, regardless of
the age of rehabilitation. However, aggregate stability was not significantly correlated to SOC
nor to erosion rates. Multiple regression analysis showed that for annual values, SOC is the
main factor controlling erosion rates in reclaimed tepetates, explaining 64 % of soil loss
variance and 79 % of runoff variance. The evolution of erosion rates is therefore dependant
on carbon accumulation rates.

After fragmentation, organic farming increased carbon sequestration rate to 0.8 Mg C ha-1 yr-
1 compared to 0.22 Mg C ha-1 yr-1 in conventional management. In plots reclaimed in 1986,
carbon sequestration ranged from 0.21 Mg C ha-1 yr-1 in conventional management to 0.37
Mg C ha-1 yr-1 in improved management and 0.61 Mg C ha-1 yr-1 in organic management.
Erosion rates in terraced reclaimed tepetates could decrease below tolerable value (< 10 t ha-1
yr-1) three years after fragmentation under organic farming, compared to seven years under
conventional farming.

Results also confirmed the key role played by vegetation cover (accounting for 27 % of soil
loss variance for single events) and emphasize the importance of crop nutrition and crop
association to control erosion. Improved management provided

Total porosity ranged from 44.8 % on average in 2003 to 50.4 % on average in 2005. We
observed no significant effect of management or age of rehabilitation on soil porosity and
pore size distribution, suggesting that high tillage intensity during the cropping season which
prevented significant changes in porosity between managements.

This three years study demonstrated that organic farming has a positive effect on soil erosion
during rehabilitation of tepetates. However, unless a market for organic products is developed
and a certification system established, we recommend organic amendments to be
complemented with mineral fertilization to ensure optimum vegetation cover and erosion
control.