This dataset contains information about meteorological conditions, ammonia concentration and deposition rates resulting from an experimental ammonia (NH3) enhancement setup in a tropical forest in central Sri Lanka. The experiment is designed for controlled enhancement of ambient NH3 concentration within the study plot under natural field conditions so that effects of NH3 on tropical vegetation can be studied. This will help identify tolerance thresholds of vegetation to NH3 as an air pollutant and determine critical levels that can be incorporated into regional environmental policy. Meteorological measurements were recorded at multiple heights on a meteorological tower. Under suitable wind conditions, NH3 was released towards two vegetation monitoring transects replicating pollution from a point source, and NH3 concentrations in the air were measured using monthly passive samplers. Continuous meteorological data, NH3 release, and NH3 concentration data are provided in 15-minute intervals and this dataset relates to measurements taken in 2023 – 2024. Deposition rates were modelled using a bi-directional resistance model on a monthly timescale based on measured NH3 concentrations in the air, micrometeorology and plant physiology. This dataset provides an extension of the 2022 dataset to enable longer term analysis of NH3 deposition and its effects in a tropical forest. The work was supported by UKRI GCRF South Asian Nitrogen Hub (Grant NE/S009019/1). Full details about this dataset can be found at https://doi.org/10.5285/449e746d-6291-4653-a3e0-b18f897abc3e