Out in the Vineyard Report Autumn 2012

Vintage 2012 will certainly be recognised as one of the great wine production years in the Margaret River wine region and this is particularly so for Cabernet Sauvignon. From my perspective we shouldn’t forget that the October, November and early December period was one of the more challenging that I have ever managed. The disease pressure (chiefly with Downey Mildew, a disease that many of us are only starting to come to terms with!) required constant attention due to inclement weather. The kind weather that followed in late December through to May and the fact that bird pressure was almost nonexistent due to the strong Marri flowering (which, by the way, is still occurring now!) has been so benevolent to grape growing that the resulting wines already show great promise.

Margaret River vintage 2012 will be recognised for its wine quality and out in the vineyard, the viticulturist and vineyard team are quietly working towards setting the agenda for the 2013 vintage!

With the grape harvest completed in late April, most Margaret River wine region viticulturists are considering post harvest vine care at the lead into the period of vine senescence and then dormancy in the vines. This is the starting phase for the 2013 vintage year.

For me, the period leading into vine dormancy is the most critical for the future vine health and performance. This is the period when vines restore the nutrients and energy consumed in ripening fruit and then set the stockpile of starches, sugars and protein that will enable bud break and strong early shoot development in the following growing period. Without the accumulation of energy within the dormant wood, simply, the vine regulates bud development in the ensuing growing period and may restrict the number of buds that are burst. Less shoots equals less bunches and low cropping vines can tend to be out of balance within the fruit to canopy ratio. The end result can be small crops of low quality grapes! We understand that strong/rapid early growth of shoots in preceding years contributes to increasing bud fruitfulness in buds retained after pruning. Strong early season growth and a balanced crop of fruit contribute to mild vine moisture stress in the period leading into veraison and it is this factor with a drying surface root system that fruit quality is enhanced. It really doesn’t take much deliberation to put the effort into post harvest vine care to increase productivity and wine quality for the future vintage.

Out in the vineyard we now turn our attention towards restoring vine health by application of drip irrigation and foliar nutrition. A trend now is to apply foliar nutrients in preference to fertigation (fertiliser applied through the drip irrigation) and to maintain irrigation scheduling until the winter rainfall occurs. The intention is to restore as much carbohydrate through the leaf photosynthesis function and to store this energy into the woody parts of the vine (including the root system) in preparation for dormancy. The root system is a major store of energy and as such we encourage a widely diffused root system across the vineyard floor. Encouraged by not over irrigating during the vine growing period or the over use of nutrition through the drip (in fact I prefer not to use the drip to provide nutrients)! The use of foliar applied chelated trace elements incorporated in solutions that contain amino and other plant attractive acids enhances uptake into the leaves and provides the mineral wealth within the vine to enable some rather complicated biochemistry. It is this biochemistry that creates protein and other quality fruit attributes in the grapes. This is a major consideration for natural wine production using fewer inputs and resulting in wines with distinctly increased viscosity and mouth-feel. Get the protein correct out in the vineyard and the grape colour, flavour, aroma and structure will result in improved wine quality.

So how do we increase the protein level in grape juice and the resulting wine?

Naturally, a good place to start is in the soil! The soil must be healthy and a good starting point is to have organic matter levels in the top layer of soil (to a depth of 150mm) better than 5% of the total soil volume to that depth; this is the topsoil! We could have a soil pH that is between 5.5pH and 6.5pH (these pH indices are expressed as it would be in water), this pH range is preferred by the beneficial microbiology in the soil and provides an environment that enables efficient biological activity, dissolving minerals as part of healthy soil function and plant health symbiosis.  The use of biostimulants such as kelp and fish extracts increases the soil protein and further stimulates microbial activity. We are accepting that this microbiology is important not only for soil health but also contributes to the symbiotic relationship that mycorrhizal fungi’s present to general plant health. We now have the ability to replenish soil mycorrhiza with the addition of freeze dried “bug” formulations added into the soil and this is quite common practice in agriculture and viticulture alike. These formulations can be applied into the soil by spraying or a more preferred method is to coat the cover crop seeds prior to planting out into the soil (the newly emerging roots of the seed become the host for the mycorrhiza and eventually these move across onto vine roots). This is the function of Versicular Arbuscular Mycorrhiza, otherwise known as VAM and we cannot underestimate the value of the interaction between these VAM and the vines with shifting nutrients and minerals between plants.  At the end of the microbiological cycle, the decomposition of these fungi contributes to the protein level in soil and eventual future protein within the vine and fruit.

Cover crops and pasture are grown in the mid-row and these inadvertently contribute to the accumulation of protein in the soil. Grasses grown on healthy and nutritious soils will have protein content that when decomposed into the soil further contributes to the soil protein. Legumes such as clovers, medics and lupins contribute naturally increased levels of protein into the soil. The legumes take in atmospheric nitrogen and through a relationship with rhizobium bacteria within the roots and complex biochemistry in the plant, store the nitrogen and the plant produces leghaemoglobins, plant proteins similar to human hemoglobin another foundation of protein in the soil that becomes available to the vines into the future.

With this knowledge of microbiology, simple amino acids and the more complex proteins in wine, it is very interesting to see and taste the positive effects on finished wines at our post vintage classification tastings.   Already we get a better understanding of why we need to adopt a more organic and biodynamic approach that protects soil health and gives sustainability to our wine production.

The resulting wines are what drive us into excellence out in the vineyard and from what I see; we are in for a very exciting future in Margaret River.

Bring on vintage 2013!

Contributed by Bruce Pearce, Viticulturist

Replublished courtesy of the Margaret River Wine Association. Become a Margaret River Wine Lover here- http://www.margaretriverwine.org.au/lovers.html


About Margaret River Discovery Tours
Sean Blocksidge is the owner operator of the Margaret River Discovery Company, an avid photographer, blogger and South West WA ambassador. In 2010 he won Western Australian Guide of the Year and his tours have been rated the #1 thing to do in Australia on the Tripadvisor website for the past two years.