Influence of reflective mulch on pinot noir grape and wine quality

Abstract

The influence of reflective mulch on Pinot noir grape and wine quality was investigated over the 2004-2005 season at Upper Moutere in Nelson, New Zealand. This trial used mussel shells as a reflective mulch to improve the balance of ripening in Pinot noir.

The mussel shell mulch had numerous effects on vine performance and sensory characteristics of the resulting wine. The mussel shell mulch affected numerous environmental, vegetative, phenological, yield and flavour parameters. Soil temperature was lower under the mulch by an average of 0.9°C, 1.4°C and 1.2°C. Canopy temperature was greater above the shell treatment by 1°C for an average of 7.1 hours per day. Soil moisture retention was increased under the shell mulch. The shell mulch increased reflected UV-B radiation on the canopy by four fold over the control. Soil analysis showed zinc, iron, manganese and aluminium all decreased compared to the Control. Microbe population under the shell mulch was reduced compared to the control. Early season shoot growth was greater in the shell mulch treatment than the control by 6.5 cm and 4.6 cm, respectively. Canopy vigour measured by Point Quadrat was not significantly different between treatments. Leaf SPAD readings were higher in the shell treatment during the ripening period by an average of 3.45 and 2.5. Pruning weights were not significantly different in 2004, however increased for mulched vines by an average of 0.19 kg. Budburst was not affected by treatments in 2005. Shell mulch advanced both flowering and veraison date during the season. Treatment influences on yield parameters were varied. Clusters numbers and berry weights were not significantly different at harvest in 2005. However, bunch weights were significantly different with the control bunches an average 13.1g heavier than those from the shells treatment. Ripening analysis from veraison to harvest showed similar brix and pH measures, however on the first sample date fruit sampled from the shell treatment had TA 2g/l less than the control fruit sample. This early difference was reduced to zero by harvest. HPLC analysis showed the fruit sampled from the shell treatment accumulated flavonols and anthocyanins differently than the control, although at harvest and in the resulting wine no differences were found through HPLC or spectrophotometer analysis. Wines were made on two separate scales - controlled micro-vinification and commercial scale and tasting notes of each are included.

Analytically wines and fruit are similar; however, distinct sensory differences are evident: As a young wine, the shell treatment has a more vibrant richer and more complex fruit structure, more into the black cherry spectrum as opposed to a red cherry character seen in the control wines. The control wine is perceived to be more one-dimensional than the shell wine and the shell treatment wine is considered to have less green and grippy tannins than the control wine. These differences tend to reduce as the wines age.