Being smart with grape nutrition

Date: 7 Nov 2018
Author: Hill Laboratories

Nutrient management in the vineyard is essential for optimising grape growth to produce high quality wine, in a sustainable way. Monitoring soil and leaf nutrient levels is therefore an important step to achieve this. Soil tests are usually done in the winter, while leaf petiole and blade tests are recommended at flowering to pre-empt any shortfall of essential nutrients for the current season's crop.

As an example, potassium (K) plays a major role in vine growth and is understood to have an effect on the acidity and colour of wine. Potassium deficiencies can be observed in the early season when soils are cold and wet and shoots are outgrowing the K supply. Potassium translocates from older to younger leaves, so that deficiency symptoms of marginal-scorch and leaf-curl appear in the older leaves first. Note, if visual deficiency symptoms are present, then vine recovery to produce a full crop will likely be compromised. Therefore, being smart about nutrient monitoring to avoid any potential deficiency makes sense.

Petiole analysis at flowering is very useful to monitor vine potassium status at that critical growth stage. Our Combined Grape profile (CGP) is designed specifically for measuring the more mobile nutrients in the petiole fraction of the leaf, as well as measuring the more static trace elements in the leaf blade. However, plant analysis is only a useful tool if sensible interpretation can be made of the test results.

Traditionally, commercial laboratories used generic “medium range” levels derived from Thompson Seedless grapes in California (1978), as locally derived values had not been published. Some years ago, Hill Laboratories took a smart approach to utilise their database to determine and quantify differences between varieties grown in New Zealand. The aim was to provide more useful information that could be used by growers to manage fertility levels.

This innovative approach in using a large database means that managing nutrient levels on a varietal basis can contribute positively to grape and wine production. Our Grape Crop Guide has full instructions on how, what and when to sample. Our technical note Grape Vine Tissue Analysis is also a useful resource available. Samples can be submitted via our sample submission app (for approved customers) – another smart tool to make testing easier.

Figure 1. Middle 50% (excluding upper and lower quartile data) range values for Potassium concentrations in petioles at flowering for different varieties. Numbers in brackets following the variety name are the number of samples included in the data analysis.

Figure 2 and 3: Screenshots from our Sample Submission App - another tool to make testing easier.