1st Edition
Subsurface Drainage of Valley Bottom Irrigated Rice Schemes in Tropical Savannah Case Studies of Tiefora and Moussodougou in Burkina Faso
This study was built to investigate the impact of subsurface drainage on iron toxicity in Tropical Savannah irrigated rice valley bottoms. The research leaned upon two complementary approaches: field investigations and designed experiments. Important results, covering several fields, where achieved. For example, It appeared that single-season irrigation schemes present higher iron toxicity and acidity risks than double-season ones – 750 up to 1800 mg/l of Fe2+ higher in the single-season scheme of Moussodougou than in the double-season scheme of Tiefora. Furthermore, a statistical analysis of flow time series (ARIMA model) data was performed. It showed that with a simple water level measurement probe installed at the main gate of the scheme, it becomes possible not only to quantify irrigation water consumption, but also to diagnose farmers' irrigation schedule, providing them a means to defuse potential conflicts due to inequity in water distribution. Finally, it was shown that subsurface drainage increases ferrous iron concentration in hematite dominant soils soil – from 935 mg/l to more than 1106 mg/l in the case of the soil of Moussodougou - but also fortunately alleviate soil acidity – from pH 5.6 to 7.3 in Moussodougou. This effect will eventually reduce ferrous iron intake by rice roots, alleviating toxicity.
1. Introduction
1.1. Background and Objectives
1.1.1. Problem Statement
1.1.2. Research Questions
1.1.3. Research Objectives
1.1.4. Expected Results
1.2. Scope
1.3. Structure of the Thesis
2. Literature Review
2.1. Tropical Savannah in Africa
2.2. Soil Genesis
2.3. The Prominence of Iron and Clay
2.4. Differences between Valley Bottom and Upland Soils
2.5. Iron Toxicity
2.6. Sulphate-Reducing Bacteria in Soils
2.6.1. The Flooded Rice Ecosystem
2.6.2. Iron and Sulphate Reducing Bacteria
2.6.3. The Bacteria Against Nematodes
2.6.4. The Reduction Processes
2.7. Subsurface Drainage
2.8. Concluding Remarks and Knowledge Gaps
3. Material and Methods
3.1. The Two Study Areas
3.2. The Site of Tiefora
3.2.1. Geographic Location
3.2.2. Population
3.2.3. Climate
3.2.4. The Dam
3.2.5. The Valley Bottem Irrigation Scheme
3.2.6. Topography and Valley History
3.2.7. The Pedology and the Reasons of Choosing Plain III
3.2.8. The Problems
3.3. The Site of Moussodougou
3.3.1. Location and Activities
3.3.2. The Problems
3.4. Project Components
3.4.1. First Component
3.4.2. Second Component
4. Irrigation Systems Prediagnoses and Update
4.1. Diagnosing and Mapping Tiefora Valley Bottom
4.2. Lessons from Valley Bottom Irrigated Rice Fields of Valley du Kou
4.3. Diagnosing and Mapping Moussodougou Valley Bottom
5. Clay and Ferrous Iron Stratifications
5.1. Soil Sampling and Measurements
5.2. Statistical Analyses
5.3. Clay Stratification Occurence
5.4. Ferrous Iron Concentration in the Rootzone
5.5. Conclusions
6. Higher Iron Toxicity Risk in Single-Season Irrigation
6.1. Soil Sampling
6.2. Measurements
6.3. Statistical Analysis
6.4. Geochemistry
6.5. Conditions Check for Hypotheses Testing
6.6. Statistical Results
6.7. Geochemical Analysis
6.8. Conclusions
7 . Clay Distribution and Adapted Drainage
7.1. Soil Sampling
7.2. Statistical Analysis
7.3. Soil Texture
7.4. Finding a Regression Model
7.5. Regression Goodness of Fit
7.6. Soil Hydraulics Analysis
7.7. Conclusions
8. Infiltration Rate Increase from Upstream in a Valley
8.1. Boreholes Preparation
8.2. Under Phreatic Infiltration Rate Measurements
8.3. Statistical Analysis
8.4. Selecting a Regression Model
8.5. Regression Goodness of Fit Checks
8.6. Cross Sectional Permeability Comparisons
8.7. Conclusions
9. Water Management Using Autocorrelation
9.1. Water Level Diver Installation
9.2. Assessment of Irrigation Water Use During the Seasons
9.3. Statistical Analysis
9.3.1. Removing Outliers and Stabilizing the Variance
9.3.2. ARIMA Model
9.3.3. Autocorrelation
9.3.4. Partial Autocorrelation PACF
9.4. Assessing the Water Use Along the Two Seasons
9.5. Assessing the Irrigation Schedule by a Seasonal ARIMA Model
9.6. Conclusions
10. Drainage and Liming Impacts on Ferrous Iron
10.1. Material and Methods
10.1.1. Bucket Experiment Design
10.1.2. Implementation of the Bucket Experiment
10.1.3. Statistical Analysis of the Bucket Experiment
10.1.4. Microplot Experiment Design
10.1.5. Implementation of the Microplot Experiment
10.1.6. Statistical Analysis of the Microplot Experiment
10.2. Results and Discussion
10.2.1. Pre-ANOVA Requirement Checks for Both Experiments
10.2.2. Post-ANOVA Requirement Checks for Both Experiments
10.2.3. Increase in Ferrous Iron but Decrease in Soil Acidity
10.2.4. Improvement of Soil Resistance to Iron Intoxication
10.3. Conclusions
11. Evaluation and Perspectives
11.1. Scientific and Engineering Insights
11.1.1. Iron and Clay Stratification in Some Valley Bottoms
11.1.2. How Hematite Soils Differ from Pyrite Soil with Mangroves
11.1.3. Permeability and Clay Analyses by Regression
11.1.4. Water Use Analysis: Critical for Irrigation Improvement
11.1.5. Microplot Experiments: Efficient to Track Soil Response
11.2. Socio Economic Impact of the Research Project
11.2.1. Tiefora
11.2.2. Moussodougou
11.2.3. Social Media
12. References
Annexes.
A. List of Symbols
B. Acronyms
C. Bucket Experiment Data Tables
D. Tiefora Farmers and Plot Sizes
E. Moussodougou Farmers and Plot Sizes
F. Microplot Experiments Data and Results
G. Samenvattting
H. Sommaire (Langue Française)
I. Sourouma (Bamanan Kan)
J. About the Author
Biography
Keïta Amadou (Bamako, 1964) followed his primary education in Mali at the Lycée Askia Mohamed. He obtained his engineering degree in Hydraulic Engineering at the National School for Engineers (ENI) in Bamako in 1987. He specialised in Agricultural Engineering at the Ecole Inter-Etats d’Ingénieurs de l’Equipement Rural (EIER, now 2iE) in year 1991. After that, he joined in 1992 the International Water Management Institute (IWMI) that implemented a project on irrigation performance assessment and diagnosis in Burkina Faso and Niger. From 1997 to 2006, Mr. Keïta became the subregional coordinator of the FAO project GCP/RAF/340/JPN, the activities of which were focused on the development and experimentation of sustainable low-cost and water efficient small irrigation systems. The irrigation systems were designed to use simultaneously surface water and shallow groundwater for small scale farming. The actions of this project were implemented in three countries: Burkina Faso, Mali and Niger. The office of the FAO project was located within the International School for Water and Environmental Engineering (2iE) in Ouagadougou, where Mr. Keïta started giving lectures in irrigation and drainage. While being coordinator of the FAO project, Mr. Keita obtained a French Master degree in physics and chemistry at the University of Ouagadougou in Burkina Faso in 2003. In year 2008, Mr. Keïta obtained a Master of Science degree in Land and Water Development at UNESCO-IHE Institute for Water Education in Delft, The Netherlands. Afterwards, he returned to 2iE and continued lecturing in irrigation and drainage. He completed a PhD in Land and Water Development at UNESCO-IHE in 2015. Mr. Keïta’s current research addresses the issue of drainage of cropland for production improvement. Iron toxicity is one of the most important challenges to rice research and production in Africa, and subsurface drainage of waterlogged valley bottom irrigated rice systems is viewed as a viable solution to alleviate iron toxicity in Tropical Savannah valley bottom soils.
