Agriculture Reference
In-Depth Information
thus winegrowers must take care that the amounts applied are not excessive for
vines. This is particularly so for pig manure, which has relatively high concentra-
tionsofCu,Zn,andMn.
Composted green garden waste from cities is also used in vineyards, as is
compost made from pomace (pressed skins and seeds from a winery, called marc
in Australia; figure 3.15). After steam distillation to remove residual alcohol and
most of the tartaric acid, a product called spent marc is available to farmers for use
as a soil conditioner, stock feed, or biofuel. However, marc or spent marc contains
significant amounts of K (range 1% to 2% of the dry weight) that can cause a
problemforwinequalitywhenusedasasoilconditionerinvineyards.Foragen-
eral improvement in soil fertility and structure, composted manures and compost
can be spread through the mid-rows at rates up to 10 t/ha and worked into the soil
in winter when the vines are dormant. For a more targeted application, compost is
spread under the vines to a depth of at least 5 cm (a rate of around 2 t/ha), serving
as a mulch that suppresses weeds, reduces soil temperatures, and slows evapora-
tion.Composttea,anorganic-richliquidthatdrainsfromacompostheap,is
sometimes applied as a foliar spray, but its benefits are not proven. Composting is
discussedfurtherin“ManuresandComposts,”chapter5.
Table 3.15 lists examples of manures and organic fertilizers acceptable in
organic viticulture. Some are by-products from animal processing, such as hoof
and horn meal, and others are plant-derived products such as seaweed extracts
that are recommended as foliar sprays. Because of their diverse sources, the com-
mercial products have a wide range of nutrient contents. As with BD preparations,
nonspecific benefits are claimed for some of these products, such as the fish meal
and seaweed extracts, in strengthening a plant's disease resistance and, when used
as soil drenches, stimulating soil biological activity. Certainly, research has shown
Figure 3.15
An example of well-composted grape marc (pomace) in an organic vineyard in the
UpperGoulburnregion,Victoria,Australia.
