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Running the Gauntlet of an Unforgiving Australian Summer

Quantifying soil moisture adds to confidence to the decision not to irrigate

Can technology add confidence to the decision not to irrigate during the height of an Australian summer?

By Mark Morris posted July 03, 2017

Summary

A large number of vineyards supplement water needs through irrigation. Some growers however have a preference not to irrigation in order to obtain an adulterated expression of both climate and soil. This preference can be tested though by the harsh Australia summers, when heat can challenge vines during important growth stages.


This case study looked at how technology could be employed to provide improved visibility of soil conditions as a proxy for vine stress. This in turn would provide confidence in the grower's decision to stay the course and not irrigate.


The result was that the grower was able to close out the season out without irrigating as hoped. The use of a technical solution provided the  required level of comfort that the crop would see the summer through without damaging levels of stress.


Keywords: terroir, irrigation, rainfed, soil tension, water, soil, stress

Backgound

The objectives of vineyard management practices will be to improve the health, growing behaviours, and general balance of the grapevine. How these in turn affect wine quality has been the subject of debated since time immemorial. The extent to which management practices impact upon wine quality is both complex and difficult to quantify and qualify.


The French have historically described this relationship via the concept of “terroir”, a term often used under different definitions. Some describe terroir as a complex idea which integrates several factors, such as  the natural environment (soil, climate, topography), biology (variety, rootstock), and the human of wine, wine-making and history. Others define terroir as a dynamic concept characterising both permanent (e.g., soil, environmental) and temporary factors (variety, cultural management, winemaking).


Vineyard management involves managing a number of interfaces that co-exists and therefore influence one another. Vineyard soils are the interface between the atmosphere and the lithosphere (the earth’s mantle). The hydrosphere is the interface between the soil and bodies of water, and the biosphere comprises the biological life of the soil (plants, animals, insects, and microorganisms).


Appreciating the intricacies of the relationship between the 'soil condition' and ‘vine quality’, and the subsequent relationship between ‘vine quality’ and ‘wine quality’ are key to the producting outstanding wines. However is practical terms, emphasis will be placed on managing the soil for optimal grapevine growing conditions, so to ensure the greatest potential for high quality fruit.


Case Study

This case study took place on a block of Pinot noir (Vitis vinifera) in a Yarra Valley, Australia (37.7780° S, 145.5280° E, elevations; 50 - 430m, rainfall; 750-950mm), vineyard, between Febuary and March 2017. The purpose of the study was to determine if soil mositure monitoring could provide the right level of confidence in terms of irrigation management, and in this specific case, a decision not to irrigate.


Three thirdEYE wireless viticulture probes were installed along a single row; the row was ~300m long running on a NE - SW axis. Probes were placed at the top, middle and bottom of row, covering elevations of 143m, 125m and 107m respectively. ThirdEYE probes are capable of measuring soil tension at depths of 150mm, 300mm, 500mm and 700mm and also record soil temperature (@150mm), canopy temperature, humidity and leaf wetness.


Measurements were taken at 15 minute intervals during the period. Soil tension (kPa) for different depths are presented in the chart sliders found below . The grower had access to a real-time dashboard displaying moisture data across the block as detailed below:

STAYING INFORMED

Throughout the growing season the grower has able to keep a close eye on soil moisture levels. Tension readings across all probes for all depths were shown on a simple to understand dashboard (right), which could be accessed from any web connected device.

Each column represented a single thirdEYE probe, denoted by the column header. Each row represented a  soil depth, moving downwards through the soil horizon; 150mm, 300mm, 500mm and 700mm

The colours provide a visual prompt to grower as to the level of moisture and to flagged potential stress . Threshold values fro the colours where selecrted by the grower. 

The first set of charts shows stacked soil tension (kPa) values for the three probes placed into Row 8. These charts allowed the grower to visualise moisture through the soil horizon.


The expansion and contraction of the bands provided a simple visual clue as to moisture conditions. Contracting bands indiciated a reduction in soil tension and therefore an increase in water avaialbility. An expanded band indicated increasing tension, and therefore a reduction in avaialble moisture.

Use the arrows on the charts to view tension at different locations in the block. Temperature and rainfall remain fixed

The second set of charts provides an alternative view of soil tension. This time all four depths are overlayed rather than stacked. The grower defined maximum tension thresholds which were then plotted on the charts. Alerts were also attached to these threshold values so that the grower could be alerted when they were execeed and again when tension dropped below the theshold values.

This case study has shown a slightly less conventional use of soil monitoring technologies. Here the thirdEYE platfrom was successfully employed to avoid irrigating, rather than its usual job of helping plan irrigation applications.


The study showed it is possible to reliably deliver real-time soil moisture updates to any web connected device, and to associated thresholding and alerting to changes in moisture levels.

Further Reading


Soil Water Tension, a Powerful Measurement for Productivity and Stewardship

http://hortsci.ashspublications.org/content/46/2/178.full.pdf


IInsights into the Relationships Between Yield and Water in Wine Grapes

http://research.wineaustralia.com/wp-content/uploads/2012/09/FS-Relationship-Yield-Water.pdf

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If you're keen to learn more about how thirdEYE can benfit your growing operation call us today

Mark Morris
Managing Director & Founder
0405 309 746

Michael Gibbs
Technology & Innovation
0411 787 135