In the warmer grape growing regions of South Australia such as the Barossa Valley, one of the keys to growing premium Shiraz and Cabernet grapes (or any grapes for that matter) is good canopy management. The canopy is the green foliage of the grapevine which has several important functions, including photosynthesis.
At this time of the year in the Barossa, January, February or March can be relied upon to offer heat waves, and these can be sustained for up to two weeks as happened in March 2008 with temperatures above 35 degrees Celsius for 15 days. In South Australia, a heatwave is defined as either 5 consecutive days with maximum daily temperatures above 35°C, or 3 consecutive days with maximum daily temperatures above 40°C.
If the vines have been encouraged to grow a healthy canopy (but not too dense as this causes other problems!), the vines are more likely to be able to shield the fruit from the sun and minimise the impact of the heat. Grapes become more susceptible to heat damage as they get close to harvest and are softening. Dark coloured grapes may get much hotter than the surrounding air temperature. Berries may shrivel or be sunburnt. All of this equates to loss of yield and quality.
So, what vineyard practices do we have to ensure a good, healthy canopy?
- The use of concentrated humates and cultured compost to establish strong biological activity and develop soil structure and humus which also improves water-holding capacity.
- Soil & vine leaf testing to ensure all essential nutrients and elements are present and in balance.
- Minimal, monitored water application to the vines via drip irrigation to ensure healthy growth but never to enhance yields .
- Annual green manure crop planted mid row after harvest to give lots of green material to provide nutrition and organic matter.
- Soil mounding and mulching undervine for moisture retention.
- Minimal vineyard traffic to prevent soil compaction.
The results can be seen in the consistent quality of our Seize the Day wines and the demand for our fruit from other well known Barossa wineries!