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

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.