The use of grape marc as compost and mulch in vineyards

The use of compost in the vineyard has many
advantages including the uterlisation of vineyard and other waste streams. For example, many
vineyards apply apply grape marc from the winery, manures from nearby feedlots, or from
garden waste collected by local councils. The use of grape marc from winery in the vineyard
closes the loop on waste. Composted grape marc provides the benefits
of compost including A neutral pH, the slow release of nitrogen,
medium to high levels of Phosphorus, Potassium, Magnesium and Calcium and efficient nutrient
utilization. Soil moisture has increased retention Beneficial soil bacteria, microflora and earthworm
activity are enhanced and physical soil characteristics improve. Un-composted grape marc may also be used in
the vineyard. A partially combusted grape marc can be used as a high organic carbon
soil conditioner which contains trace elements. If the marc has been through a steam distillation
process it is weed free and does not germinate. If you are considering using uncompacted grape
marc in the vineyard, it is important to neaturalise the pH and optimize the Carbon to Nitrogen
ratio to facilitate nutrient availability. This can be achieved by partial breakdown
of the grape marc, but will be more complete by undergoing the composting process. Uncompacted grape marc is also often high
in salts, especially Potassium, excess Potassium is detrimental to soil and vine health and
may also effect grape and wine composition. High potassium concentration in vines can
lead to high pH in the grapes. Movement of Potassium into the berry causes the release
of positive ions which increasing berry pH. High pH is associated with microbial spoilage
of wine, colour instability and premature aging of wine. Acid additions will not shift
pH sufficiently, this is due to a buffering action especially with red wine as Potassium
continues to leach from the skins. There are two ways that potassium can accumulate
in fruit. Potassium accumulation can occur directly or indirectly. Direct uptake occurs
from the soil to the vines. On the other hand, indirect accumulation can occur as a result
of changes canopy conditions. The leaves of a dense, shaded canopy will move more Potassium
into berries compared to an exposed canopy. Export and accumulation of Potassium from
shaded leaves might occur as a result of improved soil conditions created by compost, which
subsequently increases canopy density. Trials conducted in NSW vineyards investigating
the effect of high soil potassium and berry potassium and pH have found a positive relationship
between these two factors. However, the results showed that the application of mulch can increase
berry potassium and pH, but the changes are small compared with variations observed among
vineyard sites and between seasons. The long term impacts on the soil caused by
the application of grape marc should be monitored using soil analysis. The best results from using grape marc in
the vineyard can be gained from fully composted grape marc. The storage of grape marc for
long periods may be associated with fungal and odor problems and have the potential to
contribute to groundwater pollution. Composted grape marc producers a finely textured, uniform
compost that is rapidly incorporated into the soil at low application rates. Ensure
that stock piles of grape marc are located away from residences and that runoff is contained.
Consult your local government association for regulations concerning the storage of
grape marc. Additional resources to assist your decision
making can be accessed at the following websites.

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