Home' Grower : October 2011 Contents The South Australian Grower -- October 2011
SODICITY changes the size and
shape of the soil crumbs therefore
their structural arrangement in
soil. This leads to rearrangement of the
pore spaces and loss of larger pores
responsible for good aeration and drainage.
Sodium affected soil is hard-setting, more
likely to form thick crusts with few surface
cracks, and will more readily compact.
More work is required to prepare the
tilth for new crops, at higher energy costs
and wear and tear of machinery.
Cr usts also promote runoff of applied
irrigation water and rainfall. Large surface
cracks can also result in preferential flow of
the applied water which results in uneven
wetting of soil in the upper root zone.
Sodic soils tend to compact and set hard
when they dr y.
This then slows down the rate at which
irrigation and rainfall water can soak in.
Loss of water through surface r unoff and
the slower drainage makes it more difficult
to leach out unwanted sodium and salt
from the root zone.
Carrots, onions and other seed crops
cannot push through thick surface crusts.
While the stems of developing
transplants can be damaged and allow
entry of soil diseases. Poor crop
establishment and uneven growth will
result in yield loss and extended har vest
times increasing cost.
Root development impact
THE healthy root ball shown is highly
branched and has distinctive white, actively
Compacted soil layers contain less stored
soil water available for plant uptake.
This combined with poor soil aeration
results in soil lacking oxygen which roots
require to function efficiently.
In severe cases this can result in rotting
roots and the trigger for soil disease to
Effects on Soil and
Plant Growth and
IRRIGATING with water sources high in sodium is a concern
because soil structure and plant growth and development
can be affected. The condition is called sodicity. JEANETTE
CHAMPMAN, DOMENIC CAVALLARO, PHIL BARNETT AND
ANTHONY FOX outline the implications.
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Figure 1: Thick
formed in sodium
within two weeks
of preparing the
tilth for planting.
Figure 2: Healthy root ball.
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