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FoodBioSystems DTP - Using organic fertilisers to manipulate soil microbiology for improved nutrient bioavailability

Project Description


Soils are essential to food production through the delivery of bioavailable nutrients required for crop growth. Depleted nutrients are routinely replenished as mineral fertilizers at specific times of the crop growing season to promote productivity. However, this approach means that fertiliser application rarely matches crop demand, resulting in costly and often environmentally damaging over-application of mineral fertilizers. In addition, soil organic matter (the natural reserve of nutrients) becomes depleted with a resultant reduction in biodiversity. This reduced organic matter and biodiversity has essentially reduced the soils natural ability to deliver crop available forms of nutrients, increasing the reliance of food production on agrochemicals.

Organic materials often considered as a waste (e.g. residual digestate from the anaerobic digestion process of organic materials for biogas production, straw, woodchip, paper-mill sludge) may provide a valuable source of soil organic matter, with the potential to provide valuable nutrients to crops. However sufficient and functional soil microbial biomass is required to transform the organically bound nutrients into crop available forms. The quality (in terms of carbon/nitrogen ratios) and quantity of the organic matter has important implications for nutrient cycling, and influences the quantity of nutrients that become incorporated into new microbial biomass.

We will investigate novel ways to bioengineer soil organic matter through manipulating the microbiology using anaerobically derived digestates co-amended with other forms of organic materials. The intention is that this manipulation will increase the provision of nutrients to the crop throughout the year. Strategies will be investigated as to how to “feed” the soil microbiology directly, to improve nutrient delivery through the crop season. This is particularly novel as current fertilizer strategies focus on feeding the crop rather than soil microorganisms. Thus the intention is to increase soil organic matter reserves through increasing microbial biomass and biodiversity, and so re-connect the soils natural processes within the rhizosphere to improve nutrient availability.

Anaerobic digestion (AD) is a microbial process which converts organic wastes into biofuels, providing a supply of low carbon energy from renewable resources. The residual slurry (digestate) contains large quantities of bioavailable nutrients and so is of commercial interest as it can produce yields of similar quantity to mineral fertilisers. However currently much of the digestate currently goes to waste as there remains a lack of confidence from users regarding its efficacy. We intend to investigate strategies to co-amend digestate with other organic resources to direct bioavailable nutrients to the microbial biomass for nutrient release that is timed to match crop demand.

It is currently known that digestate liquor initiates a short-term increase in soil microbial biomass and activity due to a large flush of readily available nutrients within the digestate. It is likely that this response will accelerate the decomposition of organic residues with high C/N ratios and increase the quantity of nutrients immobilized into the microbial biomass, which is an integral component of soil organic matter. This process will provide a store of labile nutrients within the microorganisms in soil surrounding plant roots (‘the rhizosphere’) that can be accessed by plants through root exudation-driven rhizosphere processes.

Hence the aim of this PhD is to understand the mechanisms associated with utilizing anaerobic digestate as a rich source of labile nutrients, combined with recalcitrant organic residues with high C/N ratio, towards improving crop nutrients. Digestate is particularly interesting as it has been subjected to anaerobic decomposition and so its fiber component may represent stable organic matter. An understanding of how these materials interact with rhizosphere microorganisms, and thereby instigate the release of organically bound nutrients for crop development throughout the year, will enable nutrient strategies to be developed that will reduce reliance on mineral fertilizers.

This project is part of the FoodBioSystems BBSRC Doctoral Training Partnership (DTP), it will be funded subject to a competition to identify the strongest applicants. Due to restrictions on the funding, this studentship is only open to UK students and EU students who have lived in the UK for the past three years.

This project is a CASE studentship with FutureBiogas. This project involves a placement at the CASE funding partner, FutureBiogas, who are one of the largest producers of biogas in UK. Their digestate plants convert a wide range of digestate feedstocks into clean, renewable energy (biogas). The placement will give the candidate direct experience of the biogas industry, while enabling a platform to communicate the science. In addition, the project is supported by the Organic Research Centre (ORC), who are interested in organic forms of fertilisers and improving soil health. The ORC will provide guidance to ensure that the research is relevant to the organic farming sector, while providing opportunities to communicate the science to the farming sector.

Training opportunities: Training will incorporate a 3 month placement at Future Biogas, including workshop preparation, data analysis, communication and knowledge exchange. The PhD will include elements of training at both Cranfield and Reading Universities.

The research will utilize soil ecological principles and biochemical cycling to benefit agriculture for improved crop nutrient acquisition. Experience will be gained of hypothesis driven experimental design, including experiments in a greenhouse and field-trials. The student will learn a range of field sampling techniques.

Microbial techniques will include genotypic profiling using DNA based techniques, phenotypic profiling using Phospholipid Fatty Acid analysis, and functional profiling using soil respiration and enzyme based techniques. Nutrient analysis will include ion chromatography, segmented flow analysis, and British Standard methodologies. Training will also be given on statistical and bioinformatics approaches of data analysis. The student will be given lots of opportunity to communicate their science to both academic (e.g. Cranfield’s Environment and AgriFood Doctoral Training Network and conferences) and industrial platforms.

Student profile: We are looking for an enthusiastic graduate of environmental, biological or chemical sciences, with an interest in in soil/biochemical cycling processes. Experience of microbiology and/or ecological processes will be an advantage. The candidate should have knowledge of UK agricultural practice, with a keen interest towards developing on-farm sustainable circular solutions to waste management using organic amendments for crop nutrient requirements. The project will develop skills towards generating good quality hypothesis driven science, experimental design and implementation, laboratory skills and statistical analysis. The student should be keen to communicate their scientific findings to academia, and both the biogas and farming industry as they will be involved with knowledge exchange activities.

Funding Notes

The FoodBioSystems DTP is a collaboration between the University of Reading, Cranfield University, Queen’s University Belfast, Aberystwyth University, Surrey University and Brunel University London. Our vision is to develop the next generation of highly skilled UK Agri-Food bioscientists with expertise spanning the entire food value chain. We have over 60 Associate and Affiliate partners. To find out more about us and the training programme we offer all our postgraduate researchers please visit View Website.

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