The spatial and temporal biogeochemistry of agronomic grasslands

This long-term field trial is established on permanent grassland plots receiving different doses of animal slurry or mineral fertiliser since 1970, alongside control plots with no amendments. Periodic soil and herbage sampling over five decades enable the analysis of archived samples, facilitating a robust <br>analysis of both temporal trends and spatial variability in agronomic grasslands. Multi-elemental concentrations are determined using ICP-MS combined with XRF for soil, herbage, and animal slurries.

To observe the association between multi-elements and field trial parameters - depth, cut, block - the PCA analysis is performed. To assess the effect of different experimental treatment factors over the time-scales - animal slurry versus mineral fertilisers versus control - the advanced mixed-effects model GLM is applied. These statistical methods <br>account for spatial association and temporal trends, ensuring a holistic assessment of fertiliser input influences on elemental biogeochemistry of grassland soils.

The results, between 1972 and 2018, reveal animal slurry application markedly depleted soil Al, As, Fe, K, Pb, Si, and Ti concentrations in the topsoil layer (0-15 cm), mineral fertilisers application generally followed the same trend for these elements in this layer. Animal slurry results in a pronouncedly <br>enhanced level of Cu and Zn concentrations over 46 years of application, not enhancing the other elements. Particularly for the dissipation of As, this loss being greater for animal slurry as compared to mineral fertilisers.

Over 46 years of fertilisation management, As exhibits vertical migration within the soil depth profile. The key contribution of this thesis is advancing the understanding of how long-term fertilisation practices influence grassland element’s biogeochemical cycling through the integration of chemical analysis and ecological modelling.<br><br><i>Thesis embargoed until 31st Dec 2026.</i>