Application of the normalized difference vegetation index (NDVI) for monitoring phenological stages in grapevine (Vitis vinifera var. Torrontés Riojano)

Abstract

The monitoring of phenological phases in crops is essential for efficient agricultural management, as it allows production decisions to be adapted to the state of development of the plants. In the case of grapevine (Vitis vinifera L.), these phases reflect physiological and morphological transformations influenced by climatic, water and management factors. In this context, vegetation indices derived from satellite images offer accurate and non-invasive tools to monitor plant growth throughout the phenological cycle. This study analysed the relationship between the Normalized Difference Vegetation Index (NDVI) and the phenological phases of the grapevine variety Torrontés Riojano in three farms in the Antinaco - Los Colorados Valley, La Rioja, Argentina. High-resolution PlanetScope satellite images taken during a complete agricultural season were used. NDVI values per farm and date were calculated from these images. At the same time, field observations were made to record the phenological phase corresponding to each image. The results showed a positive relationship between NDVI and the advance of the phenological cycle, with different intensities between farms.A common pattern was observed in the three study units: slow growth of NDVI in the initial stages, accelerated increase in the middle stages, and stabilisation in the final stages, suggesting a sigmoidal evolution.Differences in NDVI levels were also identified between farms, with Farm 3 standing out with higher values throughout the cycle. This approach demonstrates the value of the combined use of satellite images and field observations for monitoring phenology in grapevine. The NDVI behaved as a sensitive indicator of the state of development of the crop, making it possible to visualise differences between production units and providing a solid basis for future applications in agricultural management.