This dataset comprises observations from treatments comparing conventional (LDPE) and biodegradable (PLA/PBAT) plastic mulch films in both new and field-weathered conditions. The dataset was generated from a controlled mesocosm experiment designed by researchers to investigate the effects of plastic mulch films on soil and plant systems. The data were collected during the experimental period and include measurements of soil properties, plant growth, nitrogen dynamics, greenhouse gas emissions, and microbial activity. Plastic materials were applied to soil at three concentrations (0.05%, 0.5%, and 1.5% w/w) and as realistic size mixtures of macro-, meso-, and microplastic fractions (1:1:1). The experiment was conducted using radish (Raphanus sativus L.) grown under controlled mesocosm conditions. Data were collected through a combination of soil sampling, plant measurements, and laboratory analyses. These include soil physicochemical properties (e.g. bulk density, moisture), plant biomass and nutrient uptake (including ¹⁵N fertiliser partitioning), greenhouse gas emissions (e.g. N₂O, CO₂), and indicators of microbial activity. The dataset captures responses across different plastic types, degradation states, and concentrations, providing a structured comparison of their effects under controlled conditions. Further methodological details and experimental procedures are provided in the lineage field and the supporting documentation. Full details about this dataset can be found at https://doi.org/10.5285/c2d4f068-e6bb-4613-8c43-e96b0aae25e8
