Leaf phosphorus concentration as a diagnostic tool for predicting grape composition in subtropical viticulture

Abstract

In subtropical viticulture, grapevines are cultivated in soils with low phosphorus (P) availability, requiring P fertilization to enhance their productivity. However, the relationship between grapevine yield and grape quality remains a matter of discussion. This study aimed to (i) investigate the effect of different rates of P application on grapevine yield and grape chemical composition, (ii) identify the trade-off between grapevine yield and grape composition, and (iii) characterize leaf P dynamics in response to P supply and use foliar P as a tool to predict grape composition. The investigation was carried out in southern Brazil, from 2016 to 2020, on 'Chardonnay' and 'Pinot Noir' (Vitis vinifera L.), fertilized with the following rates of (0, 10, 20, 40, 60, and 100 kg P₂O₅ ha⁻¹) applied from 2011 to 2015. Hierarchical Bayesian models were used to obtain the most probable relationship between yield and P concentration in leaves for each grapevine cultivar. 'Chardonnay' and 'Pinot Noir' achieved their highest probable yields at 40 and 60 kg P₂O₅ ha⁻¹, respectively. However, high grape yields triggered lower berry total soluble solids, total titratable acidity, pH; polyphenols, and anthocyanins. ‘Pinot Noir’ presented more stability for maintaining grape composition than ‘Chardonnay’ when compared at similar yield levels. Finally, the leaf P concentration at flowering resulted in an adequate indicator of soluble solids in berries, with a linear plateau association and a breakpoint for leaf P at 2.6 g P kg⁻¹. These outcomes will assist the winegrower by anticipating the characteristics of grape products.