Phosphorus critical levels in soil and grapevine leaves for South Brazil vineyards: A Bayesian approach

In South Brazil, grapevines (Vitis vinifera L.) have been grown in acid sandy soils, increasing phosphorus (P) need for fertilization. However, current fertilizer guidelines for growers are based on Vitis labrusca grown in clay soils. Therefore, there is a clear need to provide new recommendations on fertilization in vineyards. This study aimed to: (i) establish critical levels (CL) for P in the soil and grape leaves at flowering and veraison growth stages; and (ii) propose P maximum technical efficiency (MTE) rates for white and red grapevines grown in sandy soils based on a Bayesian approach. The study was carried out in sandy soil in South Brazil, with six P fertilization rates (0, 10, 20, 40, 60, and 100 kg P2O5 ha -1) applied annually from 2011 to 2015. Grape yield, P concentration in both soil and leaves (at flowering and veraison), and grape composition were measured during three growing seasons (2016, 2017, and 2018). The CL of P in the soil was 37 mg dm-3. This study is the first to propose CL for grapevine leaves at flowering (1.63 g kg -1) and at veraison for white (1.12 g kg-1) and red (1.38 g kg -1) grapevine cultivars in Brazil. Lastly, we proposed MTE rates for 'Chardonnay' (42 kg P2O5 ha -1) and 'Pinot Noir' (66 kg P2O5 ha -1). This new information provides foundational knowledge to reduce the rate of P fertilization up to 60 % for 'Chardonnay' vineyards. The utilization of this Bayesian approach has relevant implications for defining the optimal P management to be applied to vineyards around the globe.

Automated summary

This study aims to establish critical levels (CL) for phosphorus (P) in soil and grape leaves at different growth stages and propose P maximum technical efficiency (MTE) rates for white and red grapevines grown in sandy soils in South Brazil, using a Bayesian approach. The results provide the first CL for grapevine leaves at flowering and veraison in Brazil and propose MTE rates for specific grapevine cultivars. This new information can help optimize P management and reduce fertilizer usage in vineyards.