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Ecohydrological basis of vapour-fed irrigation using Super Absorbent Polymers (SAP) and related socio-economic impact

Project Description

Project summary:
This project investigates experimentally and via numerical modelling the use of SAP in promoting the condensation of brackish water evaporative fluxes from soil to assess its use for sustainable irrigation in humid and arid regions.

Crop farming, livestock and afforestation in many Arid and Semi-Arid Lands (ASAL) of the world depend on water from underground resources that is often saline (‘brackish water’). Because of increasing urbanization, industrialization and persistent pollution exacerbated by climatic changes (e.g., IPCC) water scarcity is likely to become a challenge (e.g., FAO) also in countries normally rich of freshwater resources (e.g., Scotland). Irrigation with saline water reduces the yield and quality of many crops and degrades the quality of the soil overtime (‘soil salinization’). The research team of Dr Mignard recently focused on developing improved or novel irrigation methods that allowed the use of saline water to grow crops and tree saplings, with applications in Kenya and other similar ASAL regions of the world. Following an original method devised at Edinburgh University, Super Absorbent Polymers (SAPs) buried in soil captured the moisture and condensate that was produced by the evaporation of brackish water. The experiments are at a preliminary stage and the setup is not optimised yet.

Key research questions
• How much does SAP concentration in soil favor water condensation and soil moisture increase?
• How do bottle geometrical configurations, soil grain size distribution, plant species and biomechanical properties, local microclimatic conditions and degree of salinity control the system ecohydrological functioning as well as crop growth efficiency?
• Does SAP degrade in soil and can it easily be recovered from soil?
• How much effort is required for crop planting, control and recovery?
• Is this technique efficient and can it be implemented across production scales with actual socio-economic impact?

Methodology and timetable
Via three Work Packages this project will: WP1) understand the scientific basis behind this novel and ingenious technique and optimize the ecohydrologic functioning of the system towards its promotion to practical use via experiments and modelling; WP2) quantify the risk of SAPs material degradation in time and its potential pollution impact and consequences on soil and rizhosphere processes as well as with respect to groundwater transport phenomena, and WP3) assess the socio-economical impact of implementing such a technique at different production scales.
Year 1. Literature review, training on using laboratory tools design and assembling of exper setup for exp in WP1; running exp 1 with different soil and hydroclimatic conditions, bottle configurations and crop species. Crop both above and below-ground variable will be measured and statistically analysed for comparison (cont. in year 2). Collection of soil samples for analyses of SAP concentration and degradation (WP2).
Year 2. Continue WP1 exps and WP2 SAP and soil collections, and setup and calibration of a numerical model (HYDRUS 2-3D) of the unsaturated soil system to support further virtual analyses under changing and more complex scenarios (cont. in year 3). First paper writing (WP1). Start analyses of WP2 soil and SAP degradation data (cont. in year 3);
Year 3. Ultimate numerical modelling of WP1 scenarios, analyses of WP2 data and second paper writing (WP1+WP2). Performing work-load and ergonomic analyses to quantify the amount of effort and energy required to scale up the system to medium and large crop dimensions (WP3) and assess transferability of the technique to actual production scales.

Experimental techniques, data collection, ecohydrological and stochastic modelling and statistical data analyses; Scientific programming and numerical modelling

Funding Notes

This project is funded through the E4 Doctoral Training Partnership (View Website). Please, notice that RCUK eligibility rules apply (RCUK Terms and Conditions of Training Grants)

The ideal candidate should have completed a degree in engineering, physics, geophysics, plant botany and/or biomechanics with strong attitude for experimental work and data analysis. Interests and abilities in mathematical modelling and stochastic processes are a plus.


Allbed, A., & Kumar, L. (2013). Soil Salinity Mapping and Monitoring in Arid and Semi-Arid Regions Using Remote Sensing Technology : A Review, 2013(December), 373–385.

Cao, Y., Wang, B., Guo, H., Xiao, H., & Wei, T. (2017). The effect of super absorbent polymers on soil and water conservation on the terraces of the loess plateau. Ecological Engineering, 102, 270–279.

Dabhi, R., Bhatt, N., & Pandit, B. (2013). Effect of Irrigation Water Quality on the Rate of Water Absorption by Super Absorbent Polymers, 3(10), 496–500.

DEFRA, Dept for Env., Food & Rural Affairs (2017). uploads/system/uploads/attachmentdata/file/648198/1.FCERMFundingMASTER2017v2.pdf

Müller, T., Ranquet-Bouleau, C. and P. Perona, 2016. Optimizing drip irrigation for eggplant crops in semi-arid zones using evolving thresholds, Agric. Water Manag., 177, 54-65

Yang, L., Yang, Y., Chen, Z., Guo, C., & Li, S. (2014). Influence of super absorbent polymer on soil water retention, seed germination and plant survivals for rocky slopes eco-engineering. Ecological Engineering, 62, 27–32.

How good is research at University of Edinburgh in General Engineering?
(joint submission with Heriot-Watt University)

FTE Category A staff submitted: 91.80

Research output data provided by the Research Excellence Framework (REF)

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