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Title: Sustainable agricultural land management by recycling algal biomass to land
Author: Alobwede, Emanga
ISNI:       0000 0004 7651 5254
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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High rates of inorganic fertiliser use in agriculture can lead to increased eutrophication of local water bodies. This can generate ideal conditions for algal blooms, creating anoxic conditions and detrimental ecosystem impacts. A proposed solution is to utilize the algal biomass to replenish soil nutrients, organic matter and structure and reduce the need for inorganic fertilisers that lead to algae blooms. This thesis investigated the extent to which algal biomass can improve soil quality, and the mechanisms by which any such improvements occur. Greenhouse and field experiments were conducted to test the effect of representatives of five algal species with contrasting elemental composition: (Arthrospira platensis (Spirulina), Chlorella sp., Palmaria palmata, Laminaria digitata and Ascophyllum nodosum), on soil physico-chemical characteristics and crop yield. None of the algae had an impact on soil aggregate stability. Chlorella sp., Spirulina and P. palmata showed evidence of nitrogen mineralization in both greenhouse and field experiments, with only C. vulgaris increasing yields of garden peas under greenhouse conditions. A 15N tracer study was subsequently performed, to assess the fate of nitrogen derived from C. vulgaris, into soil and wheat nitrogen pools. Results revealed a significant increase in wheat uptake of algal N after 20 days, from 0.02 mg to 0.5 mg 15N. Low 15N tracer recoveries in plants were attributed to immobilization in the soil (binding of NH4 + to clay particles) and/or microbial biomass, making it unavailable to plants. The bulk soil retained a higher amount of nitrogen (31%), highlighting the significant role microbes play in organic matter turnover, and thus prompting an in depth look into microbial communities and taxa responsible for the breakdown and cycling of the algal N. 16S rRNA amplicon sequencing revealed an increase in alpha diversity in soils treated with C. vulgaris by day 30, most likely spurred by an increase in relative abundance in taxa (Proteobacteria and Bacteroidetes) putatively involved in facilitating the breakdown of organic residues. The thesis findings provide useful insights into the application of algae biomass to soil as part of a nutrient management strategy, whereby careful consideration would be required for specifying the optimum quantity of biomass required as well as the chemical composition of the algae, as these have been shown to have strong links to measurable effects on soil quality.
Supervisor: Pandhal, Jagroop ; Leake, Jonathan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available