Agricultural Lighting Strategies in Portugal: Insights from DLI Mapping

The Daily Light Integral (DLI) maps of Portugal are decision-support tools to provide objective assessments of light availability for plants. These maps allow for the analysis of the spatial and seasonal distribution patterns of photosynthetically active radiation (PAR, 400–700 nm). A semi-automatic DLI mapping workflow was elaborated and DLI maps with two different scales (2 and 5 mol·m⁻²·d⁻¹) were created for Portugal’s mainland, analyzing from regional (Northern regions, Central regions, Southern regions) and seasonal (Spring, Summer, Autumn, Winter) perspectives. The DLI values and ranges in Portugal provide a clear spatial gradient from north to south, influenced by geographic location, topography, and climate. In autumn, the DLI values decrease (11–41 mol·m⁻²·d⁻¹) and the lowest DLI values are observed in the winter months (7–17 mol·m⁻²·d⁻¹). During spring, DLI values increase, reaching their peak in the summer months (41–57 mol·m⁻²·d⁻¹). In autumn the DLI range is narrow (11–13 mol·m⁻²·d⁻¹), as well as in winter (8–12 mol·m⁻²·d⁻¹), and it becomes broader during spring and summer (11–14 mol·m⁻²·d⁻¹). To enhance agricultural practices, future DLI maps should be integrated with agro-climatic maps and thematic layers such as soil, water, topography, temperature, and biodiversity. These integrated maps should then be incorporated into agricultural policy and decision-making to improve crop management strategies. Portugal’s agricultural lighting strategy will utilize DLI maps alongside crop-specific recommendations, shading management, local conditions and market demands.