Overview

Project Highlights:

 

  • Field and glasshouse experiments to answer applied questions
  • Join a growing and dynamic international community working on plant silicon
  • An opportunity to contribute to food security

Silicon (Si) has been described as a silver bullet for plant stress (Meharg and Meharg, 2015). It can mitigate impacts of herbivory, drought, salinity and heavy metals to increase plant growth and agricultural crop yield (Cooke and Leishman 2016). All plants take up some silicon but some species accumulate large amounts. Many of these hyperaccumulators are agriculturally significant crops (e.g. rice, wheat, sugar beet, sugarcane, corn, and barley) and can take up large amounts of Si (0.5 and 4.1% dry mass). Plants take up silicic acid from the soil solution and deposit it in tissue as amorphous silica bodies or phytoliths. However, repeated cropping can reduce the amount of plant available silicon because the removal of harvested biomass means phytoliths are not returned to the soil and recycled. The decreased availability reduces the capacity of plants to manage stress. Soils in parts of Europe, Southern Africa and Asia are now shown to be deficient in plant available Si (Vandevenne et al 2011, Carey and Fulweiler 2016) and as a result are heavily fertilised (Carey and Fulweiler 2016) to compensate.

Measurements of archived samples from a long term (1883 to 1994) wheat field at Rothamsted (UK) showed a decrease in phytoliths in both topsoil and wheat straw, yet we do not know if Si deficiency is widespread in soils across the UK. In the same study, topsoil phytolith abundance was increased through reforestation in an adjacent area, indicating that Si depletion can be reversed though land use change. There are a variety of land management practices in arable systems that could increase the input of biogenic Si to compensate for Si removed during crop harvest. In arable agricultural contexts these include the implementation of cover crops between winter and spring sown crops that could potentially provide a source of biogenic Si to close the Si cycle.

The project will investigate the following research questions:

  1. Are agricultural soils in the UK deficient in plant available Si?
  2. Could yields be raised and stabilised by increasing the availability of this beneficial nutrient?
  3. Could cover crops be used to increase plant available Si in soils?

     

     

Figure 1. Silicified stomata and epidermal cells.

Methodology

The project will involve field surveys and glasshouse experiments. To determine if agriculture has depleted phytoliths and plant available silicon in the UK and to what extent, soil plant available silicon (CaCl2 extraction) in agricultural soils will be compared to those in adjacent uncropped areas (meadows, woods, hedgerows etc). Different soil types will be measured to explore how this effects Si availability as well as land-use history. We will use the national soil database at Cranfield University to select candidate field locations.

Glasshouse experiments will measure the potential of cover crop (both diverse mixes and single species from different families) to increase the amount plant available Si for subsequent crops and increase crop yield. Both the total Si uptake of cover crops, and abundance and solubility of the phytoliths produced will be measure at the state of the art chemical analysis lab at The Open University. We will use the unique facilities at the Agri-tech innovation centre at Cranfield University. The controlled glasshouse environment has a sensor platform to also enable plant phenotyping to detect early onset of stress to different Si and environmental conditions.

Training and Skills

Through this project a student will gain a suite of skills in both soil science and plant physiology, though field surveys, a glasshouse experiment, and associated soil and plant chemical analysis all using state of the art facilities. A student will develop statistical analysis skills, particularly multivariate analyses, using the R language and environment. The student will present their research at knowledge exchange events for non-academic audiences in the agricultural sector (e.g. events such as GREAT soils organised by the levy boards and attended by agronomy companies and growers).

Timeline

Year 1: Literature review. Identify candidate field locations and conduct field soil survey and sampling. Soil chemistry analysis to determine Si availability in a selection of soil types and land uses. Glasshouse experiment planning and set up initial pilot study. CENTA training focused on foundation modules, project management and selected masterclasses.

Year 2: Develop glasshouse experiment based on outcomes of pilot study and devise appropriate statistical design and replicates. Maintain and modify experiment. Harvest and analysis of soil and plants from glass house experiment. Repeat measure or expansion of field survey as appropriate. Manuscript preparation. CENTA training focused on masterclasses, research writing and methods, non-academic communication and engagement.

Year 3: Second round of glasshouse experiment utilising the unique plant phenotyping platform in the glasshouse . Manuscript preparation and conference attendance. CENTA training focused on advance courses and work placement.

The student will be registered at the OU but during the PhD there will be a significant time spent at Cranfield (e.g. during the glasshouse experiments) where they will have access to facilities and also desk space with the Agrifood doctoral cohort. The Co-I will be responsible for embedding the student at the supporting institution.

Partners and collaboration (including CASE)

The project benefits from collaboration with Cranfield University, which also has a strong links with businesses in the agricultural sector. Agrii, a leading UK agronomy company, are potential CASE partners on this project.

Further Details

Students should have a strong background in plant biology, pedology or both, and a keen interest in fieldwork and applied science. Some prior research experience in field and glasshouse studies or soil and plant chemical analysis would be valuable. Please contact Julia Cooke (julia.cooke@open.ac.uk) or Jacqueline Hannam (j.a.hannam@cranfield.ac.uk) for further information.

Applications must include: