1. Irrigation Groundwater Quality for Agricultural Usability
in Biochar and Fertilizer Amendments among Smallholders
Irrigators in Ekxang Village, Vientiane Province, Lao PDR
Jenkins Macedo, Mixay Souvanhnachit, Sengsamay Rattanavong,
Bounmee Maokhamphiou, Touleelor Sotoukee,
Dr. Paul Pavelic, Dr. Marianne Sarkis, Dr. Timothy J. Downs
Presented at:
Graduate Students Research Conference
Department of Geography
Clark University
Worcester, MA. U.S.A.
December 2, 2014

2. Abstract
Irrigation Groundwater Quality for Agricultural Usability in Biochar and Fertilizer Amendments
among Smallholders Irrigators in Ekxang Village, Vientiane Province, Lao PDR
1J. Macedo, 2M. Souvanhnachit, 3S. Rattanavong, 4B. Maokhamphiou, 4T. Sotoukee, 4P. Pavelic, 1M. Sarkis, 1T. Downs
1 Department of International Development, Community, and Environment, Clark University, Worcester, MA. U.S.A.
2 Department of Water Resources Engineering, National University of Laos, Vientiane, Lao PDR
3Independent Consultant, Washington DC, U.S.A.
4 International Water Management Institute Vientiane, Lao PDR.
Climate change risks pose significant challenge to smallholder irrigators who rely on rainfed agriculture for their livelihoods. Increased mean surface temperatures,
varying rainfall, increasing evaporation and declining soil moistures all serve to impact productivity. Groundwater irrigation poses promising potential for agricultural
productivity and the livelihoods of smallholders. Groundwater irrigation for agriculture use requires constant water quality monitoring. This excerpt is part of a field
research, which assessed the impacts of biochar and fertilizer treatments on soil nutrients status, soil moisture, irrigation groundwater quality for agricultural use on the
growth and yield of water spinach (Ipomoea aquatica). Groundwater quality was monitored to determine the levels of electric conductivity (EC) and total dissolved solids
(TDS) determinants of salinity and sodium, calcium, and magnesium to calculate the sodium absorption ratio (SAR) to estimate sodicity. The methods involved daily
field tests to measure EC, TDS, pH, temperature, and detailed chemical analysis. The results indicate that the mean EC (0.021 dS/m; SD = 0.010) is significantly less
than the salinity tolerance threshold for water spinach (< 1.3 dS/m) and the mean TDS (12 ppm; SD = 4.5) with soil pH of 6.6. The results suggest that the irrigation
groundwater quality was suitable for agriculture and the chance of salinity was significantly low. The computed SAR 0.174 was significantly lower than the normal level
(<10) above which soil water permeability could result from sodic soil condition. The results demonstrate that groundwater use for agriculture could assist smallholders
adapt to climate change risks, but judicious use requires constant monitoring of groundwater quality and resources to increase crop yield and improve soil health.
Key Words: Salinity, Sodicity, Groundwater Quality, Electric Conductivity, Total Dissolved Solids, Sodium Absorption Ratio
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3. Research Objectives
o To evaluate whether or not rice husk
biochar inoculated with cow manure,
manure tea, and NPK amended in soil
increase soil nutrient status and improve
crop yields relative to the traditional
farming practice.
o To assessed the potential of biochar to
improve soil water availability.
o To evaluate the costs and benefits of
treatments relative to productivity.
o *To assess irrigation groundwater
quality and crop water use efficiency
for agricultural productivity.
Note: *This excerpt is focus on a section of objective 4: “Irrigation groundwater quality for agricultural use.” 2/7/2017
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4. Scientific Background & Context
o Scientific consensus of anthropogenic-induced
greenhouse gases emissions (IPCC, 2013).
o Climate change variability increased mean surface
temperature, inconsistent precipitation event, persist
drought, reduced soil moisture and decreases in
productivity (Brown & Funk, 2008; Lal, 2009b; Gregory
et al., 2005).
o Sustainable groundwater irrigation for agricultural use
pose a promising potential in drought-induced
ecosystems (Pavelic et al.,2010).
o Judicious use of groundwater resources for agriculture
requires constant monitoring of water quality for
salinity and sodicity (Ayers & Westcot, 1976; Fipps,
2003; Hanson et al., 2006).
o Monitoring irrigation groundwater quality is essential
to reduce soil salinity and sodicity to enhance crop
growth, relative potential yield, soil water availability,
and soil health (Ayers & Westcot, 1976; Hanson et al.,
2006; Fipps, 2003). 2/7/2017
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5. Source: T. Sotoukee/GIS-IWMI Groundwater Project, 2014
Ekxang Village Land Use Map
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6. Ekxang village Water Resources
Source: T. Sotoukee/GIS-IWMI Groundwater Project, 2014 2/7/2017
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7. Soil Physical Characteristics
Source: T. Sotoukee/GIS-IWMI Groundwater Project, 2014 2/7/2017
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8. Soil Texture Classification
Empirically determined using the Visual Soil Assessment approach (Shepherd et al., 2008) and the USDA Soil Texture
Calculator http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/?cid=nrcs142p2_054167 2/7/2017
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Silty Clay (10%
sand, 50 clay &
40% silt

9. Topography
Source: T. Sotoukee/GIS-IWMI Groundwater Project, 2014 2/7/2017
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10. Salinity & Sodicity Problems in Agricultural
Water Quality
Types of
Salinity
Problems
Salinity Hazard
EC & TDS
Affects plants
Flocculation; Crop growth, H2O
availability, stress, reduces crop yield
Causes saline soil condition
Sodium Hazard
SAR = Na / √(Ca + Mg)/2
Affects soils
Soil dispersion, aggregate swelling, surface
crusting, reduces hydraulic conductivity,
and restricts infiltration
Causes sodic soil condition
Source: Fipps, 2003. “Irrigation Water Quality Standards and Salinity Management
Strategies.” Agricultural Communications at the Texas A&M University System, Houston, TX.
U.S.A.
2/7/2017
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11. Irrigation Water Salinity Tolerance Levels of Some
Major Vegetables
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12. Sodium Hazard Recommended Levels
Source: Fipps, 2003. “Irrigation Water Quality Standards and Salinity Management
Strategies.” Agricultural Communications at the Texas A&M University System, Houston, TX.
U.S.A.
2/7/2017
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13. Materials & Methods
A. Salinity
a. Daily water quality field-based tests (70 days)
o Electric Conductivity (dS/m)
o Total Dissolved Solids (ppm)
o pH
o Temperature (°F)
b. Soil salinity determination
o 0-15cm (5 grams each (15) soil solution)*
o 15-30cm (5 grams each (15) soil solution)*
B. Sodicity
a. Detailed Chemical Analyses (Lab)
o Sodium (Na meq/L)
o Calcium (Ca meq/L)
o Magnesium (Mg meq/L)
C. Crop Water Use Efficiency
o Evapotranspiration Monitoring
o Daily Soil Moisture Monitoring
o Climatic Parameters 2/7/2017
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14. 2/7/2017
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15. 2/7/2017
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WEATHER STATION

16. Soil Water Balance of the Root Zone
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Source: Allen et al. 1998. “FAO Irrigation and Drainage Paper 56.”

17. Crop Water Use Efficiency & Monitoring
Note: Data snapshot 2/7/2017
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18. Irrigation Groundwater Quality Testing
Note: Data snapshot 2/7/2017
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19. Groundwater Quality Parameters
Laboratory Analysis
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Sample 1500 mL

20. Analysis & Results:
Irrigation Water Salinity & Sodicity
Parameters
Chemical
Symbols
Lab
Results
(mg/L)
Atomic
Weights
(AW)
Valences
(V)
Converted
to
(meq/L) ppm
Sum of
Cation
(meq/L) pH SAR EC (dS/m)
TDS
(ppm)
Calcium Ca 12.40 40.01 2 0.620 12.40 0.515 6.6
0.174n
s 0.021ns 12
Magnesium Mg 2.95 24.31 2 0.243 2.95 <10 <1.3 < 175
Sodium Na 7.41 22.99 1 0.322 7.41 RTh Values
Potassium K 4.10 39.10 1 0.105 4.10
Bicarbonate HCO3
2- 7.40 61.02 1 0.121 7.40
Sulphate SO4 45.70 96.06 2 0.951 45.70
Chloride Cl 1.77 35.45 1 0.050 1.77
Nitrate Nitrogen NO3-N 0.18 76.01 24 0.058 0.18
Ammonium Nitrogen NH4-N 0.21 32.00 8 0.054 0.21
Ortho-Phosphate PO4-P 0.24 126.00 3 0.006 0.24
ns = impact not significant
RTh = Recommended Thresholds Values
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21. Soil Salinity from Bulk Density Soil Samples:
Electric Conductivity (<1.3 dS/cm)
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22. Soil Salinity from Bulk Density Soil Samples:
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23. 2/7/2017
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24. The Experimental Units
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25. Discussions & Conclusions
o The levels of salinity (0.021 dS/m < 1.3 dS/m) and sodicity
(SAR 0.174 < 10) were relatively lower than their respective
recommended thresholds suitable for agricultural use.
o Significant reduction in soil salinity by depth can be attributed
to biochar addition.
o The levels of EC, TDS and pH increased due to precipitation
and surface runoff and decreased due to irrigation and
groundwater recharge.
o Groundwater quality changes over time and space, but is
subject to precipitation, irrigation systems, surface runoff, and
temperature.
o Field test should be holistic and include daily measurements of
other potential pollutants.
o Sustainable groundwater irrigation poses a promising
potential to enhance agricultural productivity in hot and dry
terrestrial ecosystems.
o Agricultural water use efficiency and water quality need to be
constantly monitored locally through participatory
engagement of smallholders in the monitoring process.
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26. Agricultural Groundwater Policy Recommendations
o Groundwater quality assessment for agricultural use should be
integrative and locally accessible to smallholders.
o Irrigation infrastructures should resonate with the needs and resources
of smallholders’ irrigators to foster maintenance and sustainability.
o Local, regional or provincial, state and non-state actors should invest in
smallholder irrigation infrastructures to enhance sustainable
groundwater usability and efficiency.
o Sustainable groundwater irrigation for agricultural use should be
equipped with monitoring stations to determine water quality for early
detection of potential pollutants and their sources.
o Smallholders should be engaged in policy formulations for sustainable
groundwater irrigation to promote ownership and systems
sustainability.
o Agricultural extension services should be sensitive to local irrigation
regimes, education, training, and the provision of resources to
smallholders.
o Smallholders are willing to adapt to new irrigation infrastructures, but
fear of failure due to financial insecurity should they attempt to change
their current agricultural irrigation systems to more efficient
alternatives.
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27. Special Thanks
To my wife and sons, I am duly grateful.
Staff, Center of Global Food Security/USAID, Purdue University,
West Lafayette, IN., U.S.A.
Faculty, Environmental Science & Policy, IDCE/Clark University,
Worcester, MA., U.S.A.
Staff, International Water Management Institute,
Vientiane Capital, Lao PDR.
Faculty & Students, Water Resources and Engineering, National University of Laos,
Vientiane Capital, Lao PDR.
Chief Administrator, International Rice Research Institute,
Vientiane Capital, Lao PDR.
Staff, Office of Sponsored Research and Programs, Clark University,
Worcester, MA., U.S.A.
Staff, International Development, Community, and Environmental Travel Grant,
Clark University, Worcester, MA., U.S.A.
Administrators, District & Provincial Agricultural & Forestry Extension Office,
Vientiane Province, Lao PDR.
Staff, Soil Laboratory, National Agricultural and Forestry Research Institute,
Vientiane Capital, Lao PDR.
Staff, Water Laboratory, Department of Irrigation,
Vientiane Capital, Lao PDR.
Academic and Research Advisors at Clark University and IWMI
Independent Consultant, Lao Translation Services
Washington, D.C., U.S.A.
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28. Bibliography
Allen, R. G., L. S. Pereira, D. Raes, and M. Smith. 1998. Crop Evapotranspiration- Guidelines for Computing Crop Water
Requirements: FAO Irrigation and Drainage Paper 56. FAO, Rome, Italy.
Ayers, R. S. and D. W. Westcot. 1976. Water Quality for Agriculture. FAO, Rome, Italy.
Brown, M. E. & C. C. Funk. 2008. Food Security Under Climate Change. Science 319:580-581.
Charcoal Remedies. The Biochar Revolution,http://www.charcoalremedies.com/charcoaltimes/0512/biochar_revolution.
Accessed: 11/20/2013
Fipps, G. 2003. Irrigation Water Quality Standards and Salinity Management Strategies. Agricultural Communications at the
Texas A&M University System, Houston, TX. U.S.A.
Gregory, P. J., J. S. Ingram, and M. Brklacich. 2005. Climate Change and Food Security. Philosophical transactions of the Royal
Society of London. Series B, Biological sciences 360:2139-2148.
Hanson, B. R., S. R. Grattan, and A. Fulton. 2006. Agricultural Salinity and Drainage. Water Management Series Publication:1-
180.
IPCC. 2013. Summary for Policymakers. Intergovernmental Panel on Climate Change, New York City, NY.
Lal, R. 2009b. Soil Degradation as a Reason for Inadequate Human Nutrition. Food Security 1:45-57.
Pavelic, P., C. T. Hoanh, M. McCartney, G. Lacombe, D. Suhardiman, K. Srisuk, and Y. Kataoka. 2010. Enhancing the Resilience
and Productivity of Rainfed Dominated Systems in Lao PDR through Sustainable Groundwater Use. International Water
Management Institute, Vientiane Capital, Lao PDR.
Shepherd, G., F. Stagnari, M. Pisante, and J. Benites. 2008. Visual Soil Assessment Field Guides. Food and Agriculture
Organization of the United Nations, Rome, Italy.
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