Cost-effective multispectral imaging system for detecting nitrogen over-fertilization under different temperatures in greenhouse sweet pepper plants

• Cablecam systems offer a controlled and stable platform for greenhouse environments. • NDVI and RVI showed correlations with %N and chlorophylls at control temperature. • High temperatures limited the sensitivity of vegetation indices. • Prolonged exposure to excess N led to oxidative stress in plants. This study investigates the effects of nitrogen (N) excess under two temperature conditions on greenhouse-grown pepper plants ( Capsicum annuum L.), using a low-cost cablecam system for proximal remote sensing. Commonly used vegetation indices were analyzed to assess plant responses under varying N treatments (Control, 2 N, and 3 N) and temperature conditions (Control and Control+5 °C). The results showed that vegetation indices exhibited a lower variability in spectral reflectance under high temperature, and moderate correlations with plant traits such as %N and chlorophyll content, particularly under control temperature. However, high temperatures constrained the sensitivity of vegetation indices in detecting variations in N status, suggesting that thermal stress limits the plant’s ability to effectively utilize and respond to available nitrogen. Additionally, while short-term excess nitrogen application enhanced vegetation indices values in the control temperature setting, prolonged exposure led to oxidative stress, as confirmed by the increase in lipid peroxidation and the reduction in total phenolic content. The low-cost cablecam system provides a practical, versatile, and easily deployable solution for greenhouse environments. Despite only allowing for the control of scrolling speed, the cablecam system, integrated with a GPS-enabled multispectral camera, enabled precise and individual plant monitoring. This approach presents an adaptable alternative to unmanned aerial vehicles in greenhouse settings, demonstrating its potential for accurate monitoring and contributing to improved stress and nutrient management strategies. This study highlights the potential of vegetation indices as practical tools for assessing plant N status in greenhouse environments, although temperature-induced physiological changes should be accounted for in their interpretation.