Vineyard nutrient budget and sampling protocols

Abstract

Context and purpose of the study – Vineyard nutrient management is crucial for reaching production-specific quality standards, yet timely evaluation of nutrient status remains challenging. The existing sampling protocol of collecting vine tissue (leaves and/or petioles) at bloom or veraison is time-consuming. Additionally, this sampling practice is too late for in-season fertilizer applications (e.g. N is applied well before bloom). Therefore alternative early-season protocols are necessary to predict the vine nutrient demand for the upcoming season.  The main goals of this project are to 1) optimize existing tissue sampling protocols; 2) determine the amount of nutrients removed at the end of the growing season.

Material and methods – Field trials were initiated in late summer 2020, and conducted through 2022 in commercial, drip-irrigated ownrooted vineyard blocks in arid eastern Washington. Three rates of K were applied in Chardonnay, and three and two rates of N were applied in Syrah and Concord, respectively. Dormant canes; whole shoots at the 5-6-leaf stage; leaves (blades and petioles) at bloom and veraison; and whole clusters at harvest were collected from each block for macro- and micronutrient analysis. Yield components and fruit composition were determined at harvest, and pruning weights were collected in winter. Vines were covered with bird nets after harvest, and leaves were collected after the first freeze for nutrient analysis. 

Results – Blade and petiole nutrient concentrations were not well correlated with higher N concentrations and lower K concentrations in blades than petioles. The P and K concentrations in early-season shoots correlated with those in blades and petioles at bloom. There was no difference in yield components between the treatments in any vineyard block. Fruit harvest and leaf fall removed significant amounts of nutrients, depending on variety, crop yield, and vintage. On average across all varieties, 22 kg/ha of N, 5 kg/ha of P, 50kg/ha of K and 3 kg/ha of Mg were removed at harvest and 6.4 kg/ha of N, 0.5 kg/ha of P, 2.9 kg/ha of K and 2.6 kg/ha of Mg were removed with leaves at leaf fall. Leaf fall constitutes an important loss of nutrients in addition to the loss in the harvested fruit. If the dead leaves remain in the vineyard, those nutrients may be available for vine uptake in subsequent growing seasons. However, if the nutrients are lost, they must be replaced through fertilizer addition to prevent the gradual buildup of nutrient deficiency and sustain vineyard productivity.