Sustainability of irrigated agriculture under salinity pressure – A study in semiarid Tunisia
Author
Summary, in English
In semiarid and arid Tunisia, water quality and agricultural practices are the major contributing factors to the
degradation of soil resources threatening the sustainability of irrigation systems and agricultural productivity.
Nowadays, about 50% of the total irrigated areas in Tunisia are considered at high risk for salinization.
The aim of this thesis was to study soil management and salinity relationships in order to assure sustainable
irrigated agriculture in areas under salinity pressure. To prevent further soil degradation, farmers and rural
development officers need guidance and better tools for the measurement, prediction, and monitoring of soil salinity at
different observation scales, and associated agronomical strategy. Field experiments were performed in semi-arid
Nabeul (sandy soil), semi-arid Kalâat Landalous (clay soil), and the desertic Fatnassa oasis (gypsiferous soil). The
longest observation period represented 17 years. Besides field studies, laboratory experiments were used to develop
accurate soil salinity measurements and prediction techniques.
In saline gypsiferous soil, the WET sensor can give similar accuracy of soil salinity as the TDR if calibrated values
of the soil parameters are used instead of standard values. At the Fatnassa oasis scale, the predicted values of ECe and
depth of shallow groundwater Dgw using electromagnetic induction EM-38 were found to be in agreement with
observed values with acceptable accuracy. At Kalâat Landalous (1400 ha), the applicability of artificial neural network
(ANN) models for predicting the spatial soil salinity (ECe) was found to be better than multivariate linear regression
(MLR) models. In semi-arid and desertic Tunisia, irrigation and drainage reduce soil salinity and dilute the shallow
groundwater. However, the ECgw has a larger impact than soil salinity variation on salt balance. Based on the findings
related to variation in the spatial and temporal soil and groundwater properties, soil salinization factors were identified
and the level of soil “salinization risk unit” (SRU) was developed. The groundwater properties, especially the Dgw,
could be considered as the main cause of soil salinization risk in arid Tunisia. However, under an efficient drainage
network and water management, the soil salinization could be considered as a reversible process. The SRU mapping
can be used by both land planners and farmers to make appropriate decisions related to crop production and soil and
water management.
degradation of soil resources threatening the sustainability of irrigation systems and agricultural productivity.
Nowadays, about 50% of the total irrigated areas in Tunisia are considered at high risk for salinization.
The aim of this thesis was to study soil management and salinity relationships in order to assure sustainable
irrigated agriculture in areas under salinity pressure. To prevent further soil degradation, farmers and rural
development officers need guidance and better tools for the measurement, prediction, and monitoring of soil salinity at
different observation scales, and associated agronomical strategy. Field experiments were performed in semi-arid
Nabeul (sandy soil), semi-arid Kalâat Landalous (clay soil), and the desertic Fatnassa oasis (gypsiferous soil). The
longest observation period represented 17 years. Besides field studies, laboratory experiments were used to develop
accurate soil salinity measurements and prediction techniques.
In saline gypsiferous soil, the WET sensor can give similar accuracy of soil salinity as the TDR if calibrated values
of the soil parameters are used instead of standard values. At the Fatnassa oasis scale, the predicted values of ECe and
depth of shallow groundwater Dgw using electromagnetic induction EM-38 were found to be in agreement with
observed values with acceptable accuracy. At Kalâat Landalous (1400 ha), the applicability of artificial neural network
(ANN) models for predicting the spatial soil salinity (ECe) was found to be better than multivariate linear regression
(MLR) models. In semi-arid and desertic Tunisia, irrigation and drainage reduce soil salinity and dilute the shallow
groundwater. However, the ECgw has a larger impact than soil salinity variation on salt balance. Based on the findings
related to variation in the spatial and temporal soil and groundwater properties, soil salinization factors were identified
and the level of soil “salinization risk unit” (SRU) was developed. The groundwater properties, especially the Dgw,
could be considered as the main cause of soil salinization risk in arid Tunisia. However, under an efficient drainage
network and water management, the soil salinization could be considered as a reversible process. The SRU mapping
can be used by both land planners and farmers to make appropriate decisions related to crop production and soil and
water management.
Publishing year
2011
Language
English
Full text
Document type
Dissertation
Topic
- Other Social Sciences
Status
Published
Supervisor
Defence date
25 November 2011
Defence time
13:00
Defence place
V:B
Opponent
- Ramon Aragues