The influence of irrigation and crop load management on berry composition and yield in Chardonnay

Abstract

Australian grape producers are facing a difficult wine market, therefore a reduction of vineyard production costs is critical. This experiment was carried out on Chardonnay under field conditions in the Riverina wine region (NSW, Australia) and included two experimental factors: irrigation and crop load. Irrigation treatments (full, reduced and low irrigation) were implemented over the whole growing season, amounting to approximately 500, 350 and 300 mm, respectively. Crop load (50% and 100%) was adjusted one week after bloom by removing clusters manually. During berry maturation berry weight and composition was assessed (TSS, YAN and phenolics), at harvest must composition and yield was determined. In addition, anatomical measurements were undertaken on the rachis from the various treatments.

Both irrigation and crop load significantly affected all berry parameters during grape maturation and harvest. Increased irrigation was associated with higher yield, bunch and berry weight as well as elevated juice acidity. On the other hand, the high-water availability resulted in lower berry sugar content, as well as lower total flavonoids and hydroxycinnamates. Crop load reduction resulted in higher berry weight, sugar content and phenolic compounds, but also lower acidity and YAN. Rachis anatomical parameters were significantly affected by seasonal water availability, with higher rachis diameter and area of conductive tissues in coming from bunches that received the increased irrigation levels. No significant differences between the two crop load treatments were found.

This study highlights the interaction between source-sink manipulations and water availability, especially in white cultivars, where the understanding of the relationships between two factors is still limited.