Discrimination of irrigation water management effects in pergola trellis system vineyards using a vegetation and soil index

Abstract

This research aims to test the discrimination of homogenized areas in traditional Galician vineyards of Vitis vinifera (L.) cv. Albariño, using a vegetation index and soil electrical conductivity and their relations with plant and soil measures (stem water potential and soil water content) and productivity and quality parameters. The study was conducted in a 4.8ha commercial vineyard (Vitis vinifera L., cv. Albariño) located in Galicia (Spain). The trellis system was ‘emparrado’, typical in this region, at 1.8m in elevation; the vines were trained to quadrilateral cordons leaving 6–8 buds per spur. Several irrigation treatments – irrigation from flowering to harvest and irrigation from budburst to harvest- were conducted during the 2015 season, where a rainfed treatment was used as the control. Images acquisition – R, G and NIR bands – was developed in veraison using an unmanned aerial vehicle. Moreover, apparent electrical conductivity (ECa) was measured in winter using a soil electrical conductivity metre (EM38) in a horizontal dipole. Soil water content measurements during veraison showed statistical significance differences between irrigation treatments (p-value=0.014) but none in the stem water potential (p-value=0.19). No significant differences were observed for production parameters. However, random forest models allowed a good estimation of stem water potential and quality parameters using topographic, soil and plant variables. NDVI details analysed, using a spherical buffer showed significant differences between treatments, especially for minimum and average NDVI pixel values. The process applied showed the capacity to discriminate between different quality grapes areas in a pergola trellis vineyards. This allows to winegrowers to have a selected vintage for several wine purposes as well as, a tool for irrigation management.