Home' Grower : September 2011 Contents 14
The South Australian Grower – September 2011
◗ Soil management
Compost can offer a range of soil benefits,
including improving crops’ access to
Compost catalyst for access to nutrients
USING compost can have some great
benefits, such as improved soil
fertility, water-holding capacity, soil
structure, increased yield and quality.
But its ability to improve crops’ access to
nutrients is often overlooked.
Compost products can be used in two
main ways: as a soil conditioner and
mulch. With organic compost now more
widely available it is a great option for
organic enterprises as well.
Soil conditioner is incorporated into the
soil to increase organic matter, or soil
carbon, and microbial activity in the soil.
Adding organic matter helps to improve
the structure and water holding capacity of
the soil. Composted soil conditioners
generally have less than 20 per cent of the
particles greater than 16 millimetres in size.
Compost mulch is usually mounded
under the vine row and helps to reduce
evaporation and moderate fluctuations in
soil moisture and temperature. Coarse
textured compost is the most appropriate
to use as mulch.
Coarse mulch has at least 70pc of the
particles larger than 16mm and fine mulch
has 20pc to 70pc of material larger than
Low carbon and organic matter levels in
soil lead to compaction, poor water
holding capacity and low levels of
In some cases, soils can have high
nutrient levels, but the soil structure is so
poor that vine roots are unable to
penetrate the soil to access nutrients.
On other occasions, nutrients may not
be in a form that vines can use.
Applying soil conditioner adds organic
matter, which improves the physical
structure and water holding capacity of soil.
The flow-on effect is that the soil is
more friable and vine roots are able to
utilise more of the available soil, giving
them more access to nutrients.
Compost mulch insulates the topsoil
under vines, helping to reduce evaporation
and temperature fluctuations and optimise
the growth of the fine roots that are
crucial to nutrient uptake.
Soil microbes can improve nutrient cycling
by breaking down organic matter and
providing nutrients in a plant-available form.
Compost supplies microbes to the soil
and provides a food source in organic
matter. This increases the activity of the
microbes already present in the soil.
Compost – both mulch and soil
conditioner – can supply nutrients directly
to vines. However, not all nutrients in
compost are immediately available to vines
and their uptake can var y greatly.
Nutrient uptake from compost is affected
by a range of factors such as climate,
season, soil type, vineyard location,
compost type and irrigation practices.
There are three key nutrients that have
been most widely studied in compost:
nitrogen, phosphorous and potassium.
The jury is still out on whether compost
mulch provides much nitrogen to the soil
From research around the world it is
thought that 20pc of the nitrogen in
compost becomes available in the first year
The rate of nitrogen release from soil
organic matter is highly dependent on soil
moisture and the drip irrigation systems
used in Australian viticulture may not
provide enough moisture to breakdown
Generally, around 40pc of phosphorus
from compost should become available in
the first year of application.
Research results on nitrogen and
phosphorus uptake are highly variable and
likely to be quite site specific.
More research is needed in this area
under Australian growing conditions.
About 80pc of the total potassium in
compost mulch will be contributed to soil in
the short-term, so crops suffering from
potassium deficiency will show improvements
almost immediately after application.
Compost also contains a range of other
important nutrients, and compost suppliers
can provide typical analysis of their
products and the nutrients they contain.
It is important to keep an eye on the
nutritional status of the soil and plants
both before and after compost application.
Monitoring both the direct and indirect
nutrient contributions of compost using
soil and leaf testing can help growers
manage vine nutrition.
Although there are many factors that can
influence nutrient release from compost,
there are some tools available to help
budget nutrient allocations.
Two nutrient calculators, one for soil
conditioner and one for mulch, have been
developed by the Recycled Organics Unit
to give an idea of what to expect from
Details: Recycled Organics Unit recycledorgan-
■ Soil increases organic matter
■ Coarse texture better for mulch
■ More research needed in Aust condi-
☛ AT A GLANCE
PEATS SOIL &
PEATS SOIL &
Ph 08 8556 5295
We sell direct to industry
horticulturalists, farmers and vignerons
Poultry manure compost ideal for:
• soil conditioning
• fertilising • water conservation
Haby Bulk Transport delivery can be arranged
Price ex yard Mannum $57.70 per ton + GST
0427 708 002
Established since 2000
Email: email@example.com | www.nuleaforganics.websyte.com.au
Composted to AS44 54
Typical analysis – Organic Carbon 29% N4.2% P2.2% K1.8% Calcium 3.6% and other minor elements
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