Background: Rice is a dominant human food but also the most water-demanding staple crop globally. This high-water use is due to its cultivation; in flooded field it requires 2-3 times more water than other arable crops. The high dependency of conventional paddy rice production on water makes this cropping system unsustainable in some parts of the world and vulnerable to water shortages. Particularly problematic for the future are regions where aquifers are being over-exploited, where climate change is predicted to negatively impact water balance in agriculture and where there is high competition for water between rice producers and other water-users. Finding means of matching rice production with current and future water availability is a critical challenge for rice-producing nations, and requires techniques that reduce water use while not impacting on yield. To address these challenges a number of water saving techniques have been developed to reduce the volume of water required for rice irrigation while maintain rice yields. One of these techniques is alternate wetting and drying (AWD). During AWD irrigation the rice fields undergo multiple rounds of flooding. Water levels in the soil are then allowed to naturally drain away, to a predefined condition, then the fields are flooded again. Work using this technique has demonstrated that water used for irrigation can be reduced by 20-40% while rice yield can be maintained or even increased (Norton et al., 2017a).
Aims: While the impact of AWD on reducing water for irrigation and the effect on yield has been studied, less is known about the impact of AWD on the soil environment. When soil undergoes changes between flooded and non-flooded conditions the redox potential will alter. Many of the nutrient required by rice plants, present in the soil, will undergo changes in chemical form and therefore changes in availability to the plant. It has been demonstrated that when plants are grown under AWD compared to continuously flooded conditions they accumulated more of some elements and less of others (Norton et al., 2017a and 2017b). This projects goal is to understand where, when and how nutrient availability is altered in the soil under AWD and in doing so explore the potential of an optimised AWD system for nutrient availability to rice plants. In addition to water management, a range of soil amendments, commonly used in Bangladesh, (e.g. organic matter) will be used in conjunction to AWD, to assess the impact these have on nutrient cycling in the soil.
Methods & Training: This project will use a range of cutting-edge techniques to determine nutrient availability in soils when managed under water saving conditions. Techniques include; diffusive gradients in thin films (DGT) multilayer chemical-imaging, which provides a high-lateral resolution (sub-mm), two dimensional mapping of in situ porewater solute fluxes (Yin et al., 2020); cryo-micro sampling of soil structure; frequency quintupled 213 nm Q-switched Nd:YAG laser ablation-ICPMS; DIFS (DGT Induced Fluxes in Sediments) model for parametrising solid-solute kinetics and equilibrium resupply; HPLC-ICP-MS for metalloid speciation. DGT substrates employing novel functionalised mesoporous silicon nanomaterials (Fang et al. 2020; Yang et al. 2020) will provide As/elemental speciation selectivity providing new geochemical insight into the soil transformation during AWD. LA-ICPMS analysis of cryo-microsampling of soil structure combined with DGT solute maps, will enable adsorption-desorption distribution coefficient (Kd) to be determined in 2D, in sub-mm scales, across key regions of interest, such as the soil-water and soil-root interfaces. This will be a first and significant advance to our understanding of how the oxidation front, as it oscillates within the soil profile changes elemental behaviours during AWD management.
Skills: For this project we are looking for an enthusiastic candidate with a knowledge of soil biology and a background in biogeochemistry or analytical chemistry.
Partner organisations: This project will be a predominantly laboratory and greenhouse-based study, but with the potential to conduct the soils sampling in Bangladesh. Soils will be collected from paddy fields in Bangladesh and will reflect the major pedological classes used in rice cultivation.
This project will be in collaboration with:
- the Soil Resource Devolvement Institute, Bangladesh; a government/statutory organization that carries out research on soil and surveys on soil quality to improve agriculture in Bangladesh.
- Bangladesh Agricultural University (BAU), the country’s premier agriculture research University.
Funding and eligibility information available here.
|Profile: Gareth Norton|
Institution: University of Aberdeen
Department/School: School of Biological Sciences
Paul N. Williams
|Profile: Paul N. Williams|
Institution: Queen's University, Belfast
Department/School: School of Biological Sciences
|Profile: Adam Price|
Institution: University of Aberdeen
Department/School: School of Biological Sciences
Norton, GJ, Travis, AJ, Danku, JMC, Salt, DE, Hossain, M, Islam, MR & Price, AH 2017a, ‘Biomass and elemental concentrations of 22 rice cultivars grown under alternate wetting and drying conditions at three field sites in Bangladesh’, Food and Energy Security, vol. 6, no. 3, pp. 98-112.
Norton, GJ, Shafaei, M, Travis, AJ, Deacon, CM, Danku, J, Pond, D, Cochrane, N, Lockhart, K, Salt, D, Zhang, H, Dodd, IC, Hossain, M, Islam, MR & Price, AH 2017b, ‘Impact of alternate wetting and drying on rice physiology, grain production, and grain quality’, Field Crops Research, vol. 205, pp. 1-13.
Yin, DX, Fang, W, Guan, DX, Williams PN, Moreno-Jimenez, E, Gao, Y, Zhao, FJ, Ma, LQ, Zhang, H, Luo, J 2020. Localized Intensification of Arsenic Release within the Emergent Rice Rhizosphere. Environ. Sci. Technol. vol. 54, pp. 3138-3147.
Williams, P. N.; Santner, J.; Larsen, M.; Lehto, N. J.; Oburger, E.; Wenzel, W.; Glud, R. N.; Davison, W.; Zhang, H. Localized Flux Maxima of Arsenic, Lead, and Iron around Root Apices in Flooded Lowland Rice. Environ. Sci. Technol. 2014, 48 (15), 8498–8506.
Yin, DX, Fang, W, Guan, DX, Williams PN, Moreno-Jimenez, E, Gao, Y, Zhao, FJ, Ma, LQ, Zhang, H, Luo, J 2020. Localized Intensification of Arsenic Release within the Emergent Rice Rhizosphere. Environ. Sci. Technol. vol. 54, pp. 3138–3147.
Fang, W.; Shi, X.; Yang, D.; Hu, X.; Williams, P. N.; Shi, B.; Liu, Z.; Luo, J. In Situ Selective Measurement Based on Diffusive Gradients in Thin Films Technique with Mercapto-Functionalized Mesoporous Silica for High-Resolution Imaging of SbIII in Soil. Anal. Chem. 2020, 92 (5), 3581–3588.
Yang, J. W.; Fang, W.; Williams, P. N.; McGrath, J. W.; Eismann, C. E.; Menegário, A. A.; Elias, L. P.; Luo, J.; Xu, Y. Functionalized Mesoporous Silicon Nanomaterials in Inorganic Soil Pollution Research: Opportunities for Soil Protection and Advanced Chemical Imaging. Curr. Pollut. Reports 2020.
This project will use a range of research methods to achieve the project goals. Experiment design will be multifactorial looking at the interaction of water management techniques across a range of soils and the interaction of water management techniques with different soil amendments. Experiments will be at the lab and greenhouse scale and will use a range of experimental approaches to determine element availability and dynamics with the soil environment.
These techniques may include:
- the application of diffusive-gradients-in-thin-films (DGT) to determine elemental solute concentrations in situ in soils;
- cryo-micro sampling of soil structure;
- Frequency quintupled 213 nm Q-switched Nd:YAG laser ablation;
- DIFS (DGT Induced Fluxes in Sediments) model for parametrising solid-solute kinetics and equilibrium resupply;
- HPLC-ICP-MS for metalloid speciation.
- These techniques will be combined with analytical analysis using inductively couple plasma – mass spectroscopy (ICP-MS) and microwave plasma – atomic emission spectroscopy (MP-AES) to determine elemental concentrations within the samples.
Expected Training Provision
During this project you will gain training in a wide range of areas and techniques. These areas include; experimental design and environmental sampling, application of techniques for measuring elements within soils using a range of dynamic techniques, and skills in data analysis and statistics. You will develop skills in experimental design, on how to design experiments that allow a hypothesis to be tested and the statistical training that will allow you to perform that analysis. You will have training in soil science so you can characterise soils, including physical and chemical properties, as well as specific guidance on the rice paddy soils of Bangladesh and the environmental factors that threaten them.
You will grain experience in running and maintaining a range of analytical chemistry instruments including ICP-MS and MP-AES. Training in fabrication, deployment and analysis of DG. Other techniques could include laser ablation operation, ICP-MS dry plasma optimisation and post analysis data processing and image construction will also be provided.
During the course of the PhD, you will also learn about meso- and rhizotron set-up, how to work and sample within and across redox interfaces without disturbing the established biogeochemistry. Whilst, imbedded in this training program will be opportunities to gain international networking management/coordination. This will provide crucial opportunities for the development of communication and dissemination skills.
In the latter stages of the project, the generated experimental data from the soil experiments will be used to parametrize in silico-based modelling of the chemo-dynamics of elemental bioavailability with AWD, amendment and soil type.
Water use for irrigation at is current rate is not sustainable in Bangladesh, and Bangladesh is not the only country to have this issue. Within Asia, it is estimated 50% of all fresh water is being used for rice irrigation. With global rice production needing to increase by 70% by 2030, demands on fresh water for irrigation of rice will only increase unless water management techniques that reduce water use are developed and implemented.
A number of technologies have been develop to reduce the input of water for rice irrigation, including AWD, but little work has been conducted on the impact that these techniques have on nutrient dynamics in the soil, and the interplay of AWD across different soil types and therefore availability for plant uptake. It is important that alterations in field management do not have a negative impact on nutrient uptake by plants or if there are issues/problems they can be circumvented with the correct soil amendment/fertiliser management.
Assessing the impact that water management, with and without soil amendments, has on nutrient dynamics in the soil will allow water management systems to be optimised not only for water use but also for nutrient uptake by plants. It will also allow the development of targeted fertiliser application.
Ultimately, the combination of optimised water management and fertiliser applications will contribute to food security while reducing the amount of water used for rice cultivation. Although, this project is focused on Bangladesh, the findings have broad translatability to all rice production regions globally.
Supervision will be based mainly in Aberdeen with Dr Gareth Norton (GN) and Prof Adam Price (AP), but with opportunities to work in Belfast with Dr Paul Williams (PW). This team have a strong collaboration history spanning ca. 20 years, evidenced with 12 existing joint publications together, with ca. 1000 citations. GN/AP are experts in the optimization of water management strategies for sustainable rice agriculture, whilst PW has been the primary developer of DGT chemical imaging in rice paddy soils. It is expected that during the project the student will spend a period of 16 weeks in Belfast developing advanced analytical techniques and working with functionalised mesoporous Si.
While at Aberdeen the student will be able to develop key skills in experimental design, soil sampling and analytical chemistry. Further bespoke training to meet the needs of the project relating to fabrication, deployment and analysis of DGT, laser ablation operation, ICP-MS dry plasma optimisation and post analysis data processing and image construction, will be provided if needed.
Academics from SRDI and BAU, will be consulted on a regular tri-monthly bases as part of the projects in country progress dissemination strategy. The Bangladesh team will also provide student training in soil science and agricultural, focusing on local scenarios and challenges. All project supervision will be conducted via both direct face-to-face support in additional to regular teleconference meetings. There will also be the opportunity to potentially travel to Bangladesh to assist with soil sampling, collection and processing.
In addition to the primary supervisor panel of GN, AP and PW, the student will also gain membership to the combined lab communities of the aforementioned supervisors. A grouping of ca. 20 students, which will provide a dynamic research environment and peer-peer support base.
Supervision allocation based on project stages.
- STAGE 1: GN, AP
- STAGE 2: GN, AP, PW
- STAGE 3: GN, PW
- STAGE 4: GN, AP, PW
- STAGE 5: GN, PW
The project will be split into 5 stages. Stage 1 and 2 will be completed by project month 6. Stage 3 will be completed by project month 15. Stages 4 and 5 will start at project month 15
- The initial stage will be the optimisation of a reproducible greenhouse system that replicates AWD at the field level. Work in Aberdeen over the last five years has developed several systems at a range of scales which can be modified to meet the needs of this project.
- Identification and sampling of key agronomically important soils from Bangladesh. Bangladesh has a wide variation in soils, and can be split into a number of agroecological zones. These soils will then be sampled in collaboration with SRDI and BAU.
- Technique development. Initial experiments will use a range of techniques to determine the impact that water management has on nutrient release from the Bangladeshi soils. Techniques will be compared and a suite of analysis tools developed.
- Development of an optimised water management system in conjunction with soil amendments. This will involve a range of different experiments looking at how different amendments effect nutrient availability and how they interact with water management and impact on nutrient dynamics.
Development of an in silico decision support tool parameterised from the data from stage 4.