Thursday, March 15, 2012

Low yields in grapevines - Vintage 2012

This season grapevine yields in McLaren Vale have been lower than average.

We speculate this is due to three things we know about.

1 - High winds. Windy conditions during flowering and ripening.

2- Soil Moisture. Irrigation gives us some control, but we are heavily dependent on having seasonal rain in Spring. This season we had lower than average rainfall in December and soil moisture began to dry out. 

3- Low bud fruitfulness. The fruitfulness of dormant buds is determined during the previous growing season
(November 2010 to January 2011).

A fourth issue has worried us this year is rising salinity in soils. Did this have an effect on vine yields?

Severe salinity.
High soil salinity levels can have drastic effects on the growth and yield of grapevine crops.

Effects of Soil Salinity

Soil salinity has three main effects:

Increasing salt in the soil will increase the osmotic pressure. This results in reduced water availability and reduced growth.

Some elements or ions, especially Sodium (Na), Chloride (Cl) and Boron (B), may be toxic or poisonous to crops.

High proportions of Sodium in relation to Calcium and Magnesium can adversely effect
soil structure, and thus limit water, air and root movement in the soil.

Salinity is caused by;

• Ground water. In most cases from bore water or recycled water.

• Natural soil salinity. Examples of this being along the lake shore at Milang in Langhorne Creek or old swampy area near Silver Sands in McLaren Vale.

• Undissolved Fertiliser (usually from animal manure), or soil amendments like gypsum.

The soil test will tell us if any of these three are occurring, or if low yields is purely a combination of high winds, soil moisture and low bud fruitfulness.


K said...

Not only was there disappointing fruitset but back in Nov the low bunch counts for our cab led to the estimation of our low yield. Could the low bunch number be due to a)the reduced light at initiatiion during the cloudy weather of 2010/2011 and b)the reduced carbohydrate reserves returned to the canes because they defoliated early following fungal infections.

James Hook said...

We agree that both a) and b), poor light during initiation and some defoliation and carbohydrate issues, reduced the potential yield for this vintage.

Hail in the north of McLaren Vale had a huge effect too.