Grapevine and cover crop spectral response to evaluate vineyard spatio-temporal variability

Abstract

The use of cover crops in vineyards is considered a management strategy that contributes to improving soil structure. Remote sensing techniques of cover crops provide information on spatial variability that can be useful in precision viticulture. This study aims to investigate soil-plant interactions using biometric data, spectral response and soil physico-chemical parameters measured across 2021–2022, with the scope of assessing spatio-temporal variations of cover crop and vineyard. These evaluations were conducted on an on-farm vineyard in a semi-arid Mediterranean environment. During the winter season (T1), the cover crop (Vicia Faba) growth was evaluated. Equally, during the summer season (T2), vineyard monitoring was carried out during the phenological stages of flowering (T2A) and grape ripening (T2B). Multispectral images acquired through unmanned aerial vehicle (UAV) were employed, and subsequently, the normalized difference vegetation index (NDVI) was calculated to obtain crops vigor maps. Through bivariate LISA cluster maps, cover crop vigor maps were compared with those of the vineyard, revealing the presence of significant positive spatial autocorrelation between the two crops. Indeed, in areas where the cover crop exhibited higher dry matter accumulation, grapevine high vigor growth was observed. The spatial association identified in surveys conducted in T1 and T2 was examined considering soil parameters. It emerged that in areas where both the cover crop and the vines exhibited high NDVI values, soil factors such as soil organic carbon (SOC) content and total nitrogen (TN) were higher. Conversely, in areas where both crops showed low NDVI values, they were associated with higher soil bulk density (BD). Moreover, in low vigor zones, higher soil penetration resistance (SPR) values were observed in both T1 and T2, contributing to limiting root elongation and thus reducing overall crop growth. Vegetative growth variability observed through vigor maps and soil physicochemical properties was evaluated through principal component analysis (PCA). Soil parameters considered within these components highlighted their influence on crop growth. This study emphasizes how soil factors directly influence the spatiotemporal variability of crops. Monitoring cover crops allows for early detection of spatial variability, supporting vine growers in choosing sustainable vineyard management techniques.