Microclimate changes caused by black inter-row mulch decrease flavonoids concentrations in grapes and wines under semi-arid climate

Abstract

In this study, black geotextile inter-row mulch, a weed control practice, was applied under a semi-arid climate to attenuate solar reflection in 2015–2017, and it concurrently increased soil temperature and fruit-zone high temperature duration and decreased low temperature duration. Inter-row mulch decreased anthocyanins concentrations in grapes in 2015–2016, and consistently inhibited flavonols accumulation in 2015–2017. Correlation analysis between microclimate parameters and flavonoids concentrations reflected the importance of solar reflection, fruit-zone high and low temperature duration, heat accumulation and soil temperature to flavonoids accumulation. Basal leaf removal, a widely applied practice to increase fruit-zone light exposure, was applied to mulch-treated grapevines to investigate if increasing incident light could mitigate the impact of inter-row mulch on flavonoids, and it had limited influence on anthocyanins whereas compensated the loss of flavonols in grapes caused by inter-row mulch. Notably, inter-row mulch wines showed less red and more yellow color than controls because of lower anthocyanins concentrations.