Assessing the mineral nutrient flow and microbial activity in pasture soils

  • Tuğba Isık

Student thesis: Master's ThesisMaster of Science by Research (MScR)


Soil is a mixture of various mineral and organic nutrients that serve as the primary nutrient base for plants and animals. The fate of these nutrients and their distributions in soil reflects the soil environmental quality. Microbial communities are particularly important for ecosystem dynamics as they are involved in biogeochemical cycling of micronutrients. However, their distribution through the soil profiles and size vary with the several physical properties such as depth of soil, soil pH and organic matter. Because microbial communities may be characterised by phospholipid fatty acid (PLFA) and glycerol dialkyl glycerol tetraether (GDGT) lipid signatures, the analysis of these lipids can provide information about the structure of microbial communities in soil.
This thesis reports the results of a study about the microbial community structure and micronutrient availability in soils of identical origin but with different soil physical properties. The main aims of this investigation were to: (i) correlate the changes in microbial communities with the distribution of micronutrients in soil profile, and (ii) assess the effect that grass root type has on the vertical distribution of micronutrients and microbial activity, and (iii) the effect of soil pH on nutrient availability and microbial community size and composition whilst incubated with sheep-manure.
Overall, the topsoil supported a larger microbial community which decreased with soil depth. However, the grass root type affects the microbial community and micronutrient distribution with deep-rooted grasses providing a distribution of nutrients through the soil profile. Exogenous manure addition to the soil affects the microbial community diversity by shifting the soil pH and large changes were observed in low pH soils because of the initial pH difference between soil and manure. Soil pH was observed to have a strong effect on the available micronutrients even in the control soils such that acidic soils are likely to have higher Cu, Fe, and Zn concentrations and lower Ca, K, Mg, and Mn concentrations, whilst the overall microbial community size does not change that specifically with soil pH.
Date of Award23 Jun 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SponsorsThe Republic of Turkey Ministry of National Education
SupervisorIan D Bull (Supervisor) & Heather L Buss (Supervisor)


  • Microbiology
  • Weathering
  • Analytical chemistry
  • Geochemistry

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