A horticultural medium established from the rapid removal of phytotoxins from winery grape marc

Abstract

Grape (Vitis vinifera L.) marc has long been utilized as a compost feedstock. However, this process takes an extended period of time due to the phytotoxic chemical composition of the marc. Removal of these compounds presents an opportunity to utilize the grape marc as a growing medium. Following a water-based extraction procedure to remove polyphenolic compounds of interest, analysis of the depleted marc showed a decrease in the content of these compounds, and in nutrient and trace element levels. Carrot (Daucus carota L.) and corn (Zea mays L.) seedling emergence in the depleted marc and blends with compost were not adversely affected, demonstrating its effectiveness for growing plants at all ratios. A 50:50 blend of compost and depleted grape marc resulted in plant growth equivalent to the compost alone. This combined with the observed water holding capacity suggests that depleted grape marc, when blended with compost, can be a suitable alternative to peat or coconut coir for seedlings.