Agriculture Reference
In-Depth Information
Straw mulch in vine rows, Barossa Valley, South Australia. Photograph by the author.
Figure 7.9
• Mulch shades the soil, reducing temperatures and soil evaporation during
the summer.
• The extra organic matter and moister surface soil encourages biological
activity, especially by earthworms.
• Mulches suppress weeds.
• By preventing the breakdown of the soil structure under the impact of rain,
mulches enhance water infiltration.
The effect of mulches on soil evaporation is more important when the vines
are young and during early summer before the canopy has fully developed, that
is, when the
Leaf Area Index
(
LAI
) is low. The
LAI
is defined as
Canopy leaf area
LAI
(7.4)
Area of soil surface associated with that canopy
When the
LAI
1, as much as 70% of the total evapotranspiration is soil evap-
oration. But at full canopy development (
LAI
4), soil evaporation accounts for
only about 10% of the total evapotranspiration.
As discussed in section 5.7, there is currently a strong trend to make viticul-
ture more sustainable through better use of waste materials and less chemical in-
tervention. To this end, composts made from a variety of materials, including po-
mace from the winery, are being used as mulches in vineyards. Mulches in the
vine rows might encourage the survival of the fungus
Botrytis
, which causes bunch
rot in grapes. However, evidence from New Zealand suggests that if a fungus from
the genus
Trichoderma
is inoculated into the mulch,
Botrytis
is suppressed. Mulch
can also increase the risk of frost damage in susceptible areas (section 3.5.2).
