Three lessons from dry-land wine-growing!

I’ve been involved with many vineyards over my years of grape-growing and winemaking, and they all have their own unique terroir. Varying greatly in their rainfall each year, the soils are different, the sunlight is different, the varieties growing in them are different and so they all require slightly different management strategies.

We have had a few severe droughts in South Eastern Australia over the past 20 years, none was worse than the drought of 2006/07. In Heathcote, Central Victoria, we had very little rainfall over the winter months. 27mm to be exact from mid May through to early September. The summer was no better as no rain was to come at all. Day after day of blistering sunshine dared the vines to grow, but there was not fuel in the ground to allow them. It was unbelievably dry. Then in the winter of 2010 and right the way through until April 2011 (including harvest), the skies opened and we had the wettest period for more than 100 years. Over 1000mm fell during the growing season bringing with it disease pressure unlike anything I had seen in my 20 years of growing grapes.

Operating dry land vineyards duing these devastating droughts and floods has definitely made me a much better Viticulturalist. Seeing how one vineyard copes with extreme conditions, while others do not allows some perspective. Here are three lessons that I have learned:

LESSON 1 – Maintain soil structure by never turning it.

Soil structure is destroyed by the act of turning the soil. Sure, loose soil particles on the soil surface make it very easy to place seed in it for a crop to emerge, but it does this at the behest of maintaining soil profile. For thousands of years, soils have been sprouting life above the surface, and cycling life below the surface. By turning the soil, you are destroying the soils ability to breath. Soils operate best when a diversity of plants living in them readily allow infiltration of oxygen and water. In a vineyard this means shallow and deep rooted species of native grasses that allow water to penetrate the soils surface and move into the lower layers more readily. It also allows cycling of nutrients via worms and soil biota decomposing dead plant matter on the surface and dragging the nutrient dense decomposition further down into the soil profile.

LESSON 2 – Alleviate compaction by deep ripping every second year

Compaction creates a hard layer on the surface so that plants cannot grow easily and water cannot infiltrate through the soil profile. In dry years it creates hard-pan which stops water reaching lower soil layers, and in wet years it creates anaerobic conditions, keeping water in the surface layers and drowning soil microorganisms and the vine roots underneath. Great vineyards where complex flavours are developed all have one thing in common – great drainage! Whether it’s because they are planted on the side of a hill, or because the surface soil layers allow water to infiltrate to its sub-layers easily. In years of drought, you want any water falling on your vineyards to reach the vines roots. In wet years, you want the water to drain through the soil and not suffocate your vines. By deep ripping in the dry of autumn, you create soil cracking not only from the rip line but from the upward pulling pressure exerted on the soil either side of the ripper. This opens hard soil up so that water can drain through the profile. It also allows plant roots to explore this newly opened area, giving life back to once dead soil. The winter rains allow the soil to settle back down naturally, and the ripping doesn’t disturb the native grasses growing in it so they continue to do their thing.

LESSON 3 – Give vine shoots space!

This means leave less buds at pruning! In very dry years, a vines ability to grow and maintain leaf area is compromised. If too many buds are left at pruning, and too many shoots are allowed to grow, each shoots length will be severely restricted, compromising the vines ability to protect its fruit from the sun. The limits the vines ability create bunches of adequate size, limiting the size of the berry. Wines made from very small (pea sized berries) are often way too tannic and have high sugars, have very little flavour complexity, and often display a sweet/sour character.

In wet years, shoots that are too close create congestion. Congestion stops the flow of air and light through the canopy. The fruit is developing in a dark and often damp environment, causing fungal pressure, and becoming a haven for insects and other pests. It is also very difficult to prevent or eradicate problems because any sprays used are unable to penetrate the dense layers of leaf. Consequently the wines made from these grapes are weak in colour, aroma and flavour.