Preliminary results on the effect of different organic mulching on wine polyphenol content

Abstract

AIM: Soil mulching is an interesting strategy to reduce soil evaporation, assist in weed control, improve soil structure and organic content, increase soil water infiltration, and decrease diurnal temperature fluctuations. However, little information is known about the influence of soil mulching on grape and wine phenolic composition. For this reason, the study aimed to analyze the effect of different mulchings and soil management tecnhiques on the wine phenolic profile (phenolic acids, flavanols, flavonols, stilbenes, and anthocyanins) on ‘Tempranillo’ grapevine (Vitis vinifera L.).

METHODOLOGY: The research was carried out in two different fields, one located in Logroño and the other in Aldeanueva de Ebro (La Rioja, Spain), each one characterized by different soil conditions, weather and crop management techniques (conventional in Aldeanueva de Ebro and ecological in Logroño). In both sites, five diferent mulching techniques were applied in the row: grapevine pruning debris (GPD), spent mushroom compost (SPCH), straw (S), interow (I) and herbicide (H) treatment. Each treatment was performed in triplicate (n=3) and each replicate was vinified separately. Wine phenolic composition was analyzed by UHPLC-DAD-ESI/APCI-MS/MS.

RESULTS: Overall, in this first year of the study, mulching treatments led to only few differences between wines and the phenolic composition of the treatments was not the same across the fields. In Logroño, wines from the I treatment had higher concentration of flavonols than wines from H, while no significant differences were observed between wines for the remaining parameters. In Aldeanueva de Ebro, no significant differences were observed between treatments for any parameter, although wines from SPCH treatment tended to have fewer polyphenols. Although no statistical differences were observed between treatments, it is interesting to see that in Aldeanueva, phenolic composition increased for all groups (fewer stilbenes). Indeed it is necessary to investigate more deeply this behavior. Among other factors, this differences between fields could be due to different crop management tecnhiques.

CONCLUSIONS

In conclusion, mulching treatments had no significant effect on wine phenolic composition in the first year of the study. However, mulching treatments do not have immediate effect and probably their influence could become more significant in the following years. Therefore, further research should be performed in order to assess the long-term effects of these treatments on wine phenolic composition.