Agriculture Reference
In-Depth Information
otherwise be lost and to solve a waste management problem. The compost can be
used as mulch in the vine rows.
The disposal of wastewater from large wineries must also be properly man-
aged to prevent contamination of water supplies. For example, Riverina Wines in
the Griffith Region of New South Wales crushes 40,000 t/yr and produces 64
ML of wastewater. Two hectares of laser-leveled land, with pipe drains at 10-m
spacing and 1.2-m depth, are used to “filter” this wastewater, with the drainage
being discharged into waterways. After allowing for about 1000 mm/yr of evap-
oration from the holding lagoon, approximately 85 mm of wastewater has to be
applied every 2 weeks, which means that the soil must have a good infiltration
capacity.
The application of winery wastewater to land may cause problems because of
the relatively high concentration of salts (800-1800 mg/L), high SAR values (3-11
mmols charge 1/2 per L 1/2 ), and low pH (4.5-5). Thus, to achieve sustainable man-
agement of wastewater in the long-term, the susceptibility of the soil to saliniza-
tion, sodicity and pH change should be assessed.
Nutrients and Water Quality
Because vines are dormant during the winter and are not absorbing nutrients,
NO 3 is vulnerable to leaching from the soil through winter and early spring.
However, the presence of a winter cover crop, especially a cereal or grass, reduces
the potential for NO 3 leaching. The leached NO 3 may reach surface waters
and groundwater that are used for domestic purposes, for which the NO 3 con-
centration should not exceed 10 mg N/L (United States and Australia) or 11.3
mg N/L (Europe).
Phosphate ions are not readily leached, but they are carried by soil particles,
especially clays, that are washed into surface waters by erosion. Once in the wa-
ter, P ions are progressively desorbed from the sediment and may raise the P con-
centration above the acceptable limit of 0.05 mg P/L. The enrichment of streams,
dams, and lakes by N and P leads to eutrophication of the water body, usually
manifest by sporadic “blooms” of Cyanobacteria or blue-green algae (section
2.3.2.1). These algae may release toxins that kill fish and other animal life. When
the bloom subsides, decomposition of the large amount of dead organic matter
consumes all the dissolved O 2 , leading to anaerobic conditions and additional fish
deaths. Eutrophication, therefore, disturbs the natural balance of the aquatic
ecosystem and creates serious problems for water-treatment plants.
The quantity of P removed by erosion depends on the soil P content and the
amount of sediment transported. Quantities range from 0.1 kg P/ha/yr in a
well-managed vineyard to 1-5 kg P/ha/yr if erosion is severe ( 10 t soil/ha/yr).
The quantity of NO 3 -N leached depends on the drainage passing below the root
zone and on the NO 3 concentration of that drainage water. Drainage during the
summer depends on whether the vineyard is irrigated and how efficiently water
is applied and used by the vines. Drainage during the winter depends on the sur-
plus winter rainfall, defined as rainfall minus evapotranspiration (see equation
6.10). Some examples of potential NO 3 -N leaching in vineyards are given in
table 7.6.
7.6.3
 
Search WWH ::




Custom Search