The data consist of leaf extension rates of seagrass growth as the primary response variable; elemental and isotopic compositions of seagrass above- and below-ground biomass; seagrass morphological parameters; site-characterisation environmental parameters and temperature recorded over the experimental windows. This dataset contains in-situ experimental information relating two separate nutrient enrichment experiments that were conducted in January/February 2022 and January 2023 over 2-week periods. The experiments were designed to understand the growth response of seagrass to elevated nutrient concentrations relative to controls plots. We used agricultural fertilisers to elevate local concentrations. In 2022, we used a slow-release fertiliser and compared growth response rates at two contrasting site types with 3 treatment levels (Control, Low N and High N). In 2023, we used an all-purpose granular fertiliser, the same 3 treatment levels but varied how the fertiliser was delivered to the seagrass, i.e., water-column diffusion vs below-ground diffusion. Both experiments were conducted on the same island of Gan, in Laamu atoll, Maldives. The work has been undertaken has been funded by the GCRF-UKRI South Asian Nitrogen Hub and enabled through the University of Edinburgh and Maldivian non-governmental organisation, Maldives Resilient Reefs. Full details about this dataset can be found at https://doi.org/10.5285/8760a6d4-b9df-406d-b910-678ab0f6557f