Effect of the shade generated by simulated solar panels in two row orientation on the physiology and productivity of Vitis vinifera L. cv. Malbec

Abstract

Context and purpose of the study. In regions where grapevines are grown under irrigation, like most regions in Argentina, the wine industry should adopt more sustainable strategies and production systems towards a higher water use efficiency and a reduction in no-renewable energy consumption. To contribute to these strategies, an agrivolatic trial was started in 2020 in a vineyard at INTA Mendoza Experimental Station. Agrivoltaics combines in the same site agricultural production with energy generation by solar panels installed over the crop.

This study compared the microclimate, physiology and productivity of vines under the partial shade (47%) generated by simulated photovoltaic panels with vines without shade grown in North-South and East-West row orientation.

Material and methods. The experiment was installed in a vineyard planted in 2011 with cv. Malbec. During 2020, solar panels were simulated installing shade nets over the rows covering 47% of the surface. The transmittance of the nets was 0%. The experiment consisted in two treatments, with two levels each, radiation, with shade (SH) and control (C), and row orientation, with North-South (N-S) and East-West (E-W). For each treatment level: SH/N-S; SH/E-W; C/N-S and C/E-W there were 3 repetitions, in total 12 plots under study.

Canopy microclimate, water consumption, vegetative growth and yield were measured. Midday leaf water potential was used to decide irrigation.  At harvest (24°Brix) the content of total polyphenols and anthocyanins per berry was measured by spectrophotometry. After harvest the wines from each replicate were elaborated and anthocyanin contents were measured by spectrophotometry. FTIR spectroscopy was used to measure pH, total acidity and alcohol. Wines were analyzed by a trained panel on descriptors previously selected.

Results. The accumulated intercepted radiation on shaded canopies was 45% less than the controls plants and average daily temperature was 2°C lower than the controls throughout the season. Plants under shade regardless of row orientation required 31.7% less water than those without shade. Grapes from shaded vines were harvested four days later and yielded 25.4% less than control vines.

No differences were found in the content of polyphenols and anthocyanins per berry at harvest. Wines from shaded vines showed higher levels of total acidity and less pH and % alcohol than those without shade.