ASSESSING CONNECTIVITY INDEX IN VINEYARDS WITH DIFFERENT INTER-ROW MANAGEMENT TECHNIQUES

Oltrepò Pavese is a sensitive area of Lombardy Region, here the main land use in hilly area is devoted to vineyards, indeed viticulture is a key sector in the economy of the area and one of the most productive reality of Italy. Slope instabilities are very common phenomena in Oltrepò Pavese due to its geological and geomorphological settings that mostly consist in clay and marls formation in a complex structural setting. Understanding how the main land use could influence slope instabilities is a vital step to mitigate these phenomena that usually causes severe damages and economic losses. This study is part of wider research project named VIRECLI, sponsored by Regione Lombardia, that aims to characterize spatial and temporal vineyard variability in order to promote decisional systems oriented at vine balance monitoring, soil protection, and adaptation to climate change by using precision viticulture techniques. The focus of this work is on inter-row management techniques in two test sites, the permanent grass cover in Pernice (PER) vineyard and the alternate tillage in Vigna del Fico (VDF) vineyard, and the influence of these managements on soil properties, soil erosion and slope stability. The two test sites are investigated with field surveys comprising soil profiling and sampling, laboratory analyses on sampled soils, geophysical survey with Electro-Resistivity Tomography technique and remote sensing analyses. Laboratory analyses on soil samples assessed similar pedological settings in the two test sites, with a water table situated in the altered marly bedrock, situated at an average depth of 1.5m, that can rise to superficial horizons after intense rainfalls. There is no detectable evidence that alternate tillage and permanent grass cover management techniques affect Porosity and Saturation degree in this pedological contest. However the comparison between grass covered and tilled rows in VDF1 and VDF2 show that water content is 5% higher in grass covered rows than in tilled ones, and that VDF average water content is 5% higher than PER, with a marked difference of 10% in the first 20 cm. This could be interpreted as the consequence of the denser grass cover root system developed in the permanent grass cover inter-row management that require more water than in the alternate tillage management. The analyses on land use changes shows an average increase in parallel vineyard compared to perpendicular ones and a general increase in total area occupied by woods. ERT surveys were fundamental to characterize the test sites vineyard, in particular to reconstruct the presence of water and geological features underground. Low resistivity values, reflecting higher water content, are observed in the altered marly bedrock, confirming field and laboratory analyses. The oscillation of water table over the bedrock produce alternating condition of oxidation and reduction that have been observed in the eluvial horizon that shows the typical red and grey colour alternation. In VDF vineyard ERT shows the presence of surfaces of rupture generated by slope instabilities. These surfaces favour water infiltration in the bedrock causing zone of hydric stress in surface, moreover the presence of these fracture in superficial layer have been observed also in soil profiling where slickenside have been observed in clay horizons. Curvature maps also show that VDF vineyard is affected by the presence of a deep landslide that probably generate the soil instabilities revealed by ERT surveys. At vineyard scale flow paths are clearly showed in PER test sites where the directions are highly affected by the orientation of rows and by topography. Regarding connectivity index analyses the results are encouraging also if further study should be promoted in order to develop more detailed analyses that could correctly model the interrow transport of sediment inside and outside the vineyard.