Lending our established vines a hand when the season isn’t too kind…
While our new Climate Change Vineyard has been designed, planned and created in a way that maximises the natural forces of waterflow – many of the 30+ year old vines here at Tinja need a little assistance these days to ensure that they are producing the best fruit possible.
Blocks 2-9 (our Shiraz, Zinfandel, Merlot, and Cab Sav) were established without supplementary irrigation and are referred to as unirrigated vines (or dry-grown vines). As a result, some of these vines boast root structures that descend up to 4.5 metres, drawing from water reserves deep into the ground. Without any supplementary irrigation, these ‘dry-grown’ vines rely on adequate winter rainfall (effective rainfall) to replenish these water reserves so that they can utilise them in the growing season.
This was ever-apparent in the last drought – where long periods of no rain really dried things out. The subsequent harvest also bore these scars too; low yield and poor fruit quality. Which got us to thinking, how can we assist these vines to perform at their best, regardless of what mother nature throws our way.
Ever data-drive, David analysed past effective rainfall data from years of great quality and yield, to determine the optimal levels of rainfall needed to adequately supply the ground and vineyards. And once we had our ‘secret sauce’ we set about implementing it across Tinja.
Definition: Effective Rainfall
When we refer to ‘effective rainfall’, we are referencing rain that actually becomes available for the vines. Effective rainfall, in our case in unirrigated vineyards (i.e. deep rooted vines), is essentially winter rainfall, that is able to penetrate deep into the ground and replenish the water reserves that the vines will use.
During the summer, the ground is dry on the surface so it is absorbed here, not making it down to the roots. Much of the rainfall is taken by competitive weeds and their shallower root system. Evaporation due to warmer temperatures and sunlight also acts fast, making summer irrigation not viable for those with deep roots.
Enter our K-Line
While not rocket science in the slightest, our K-Line comprises of 10 ‘pods’ along 125 metres of low-density hose – capable of irrigating 0.2ha of vineyard at a time. This system was chosen specifically as it is easy to move (given the robust ‘pods’ can simply be towed to move to another area), and is a more cost-effective and less permanent irrigation system (a very challenging task in our ‘bush-vine’ blocks too).
Mimicking rainfall, we typically run the system for ~22 hours in each spot, equating to ~90mm of rainfall. This however is adjusted on a ‘block-by-block basis, taking soil type, moisture-holding capacity, and weekly rainfall conditions into account – as the purpose is to only provide what is necessary to reach saturation point (just before water begins to pool/run-off).
Slow and steady watering means that water penetrates deep into the soil profile, not only filling up the grounds reserves for the growing season, but also aiding growth below ground during the dormancy period.
Apart from the above benefits, there are a range of positive outcomes that result from maintaining an effective rainfall level.
- Biodiversity & Biodynamics – A saturated soil profile increases the effectiveness of our BD preparations by aiding microbial proliferation and movement, resulting in a more resilient and diverse microbiome.
- Cover Crop – Watering throughout this period means that cover crops are more abundant, increasing the feed for our sheep, as well as increasing the sugar that is effectively ‘dumped’ by the termination of the root system.
We have been using our K-Line system through winter this year due to less-than-average rainfall across Tinja. With a couple of -5°c days thrown in, and we have seen mornings where the vines are transformed into a winter wonderland! Not to worry however, as the ice that forms can help by killing pests – and as it melts, it continues to slowly saturate the ground in a similar fashion to how it would have done if it hadn’t frozen in the first place.
A -5°c morning at Tinja