Best soil management practices

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					                                                                             BEST PRACTICE GUIDELINES FOR GROWING VEGETABLES

                                       Best soil management practices

                                       Decide how to best work your soil                  Soil nutrition
                                       based on your soil type(s) and the
     Your soil is a                    present conditions. Get to know
                                                                                          If test results show your soil to be
                                                                                          strongly acidic — with a pH (CaCl2
     precious and                      your soil by digging holes or
                                                                                          method) less than 5 — then
     valuable resource                                                                    incorporate lime or dolomite into the
                                       Inspect and evaluate your soil by                  soil (refer to NSW Agriculture’s
     that is easily                    digging a hole to at least 30 cm                   Agfacts AC.19 Soil Acidity and
     damaged. Learn all                and studying the profile closely.                  Liming and AC.15 Liming Materials).
                                       Remove a block or slice of soil with
     you can about it by                                                                  Use regular soil tests to help
                                       a spade and look for roots, cracks
                                                                                          determine crop fertiliser needs.
                                       and channels, and signs of
     taking the time to                                                                   Follow the guidelines in NSW
                                       compaction (often just below the
                                                                                          Agriculture’s Agfact AC.21 Fertilisers
     examine and observe               plough layer).
                                                                                          and the Environment to minimise the
     it under different                                                                   risk of fertiliser nutrients contaminating
                                                                                          waterways and groundwater. The
     conditions.                                                                          use of a balance of manufactured
                                                                                          and organic fertilisers is often best;
                                                                                          the former provide immediately
                                                                                          available (but more easily leached)
Your soil is a precious and valuable                                                      nutrients, while the latter release
resource that is easily damaged.                                                          nutrients more slowly over a longer
Learn all you can about it by taking                                                      period and also provide some
the time to examine and observe it                                                        organic matter.
under different conditions. Maintain                                                      The use of legumes in either a crop
and improve your soil by adopting                                                         rotation or as a green manure crop
the practices outlined below.                                                             adds nitrogen and organic matter to
                                                                                          the soil.
Soil examination and
                                                                                            See the ‘Best Crop Fertilisation
Learn more about the chemical and      For more information order a copy of NSW             Practices’ section (page 31) for
physical properties of your soil by    Agriculture’s poster ‘How to read your soil’.
                                                                                            more information.
having it regularly tested.


Managing soil structure                        pesticides are absorbed on soil                • reducing the number of tillage
                                               particles, and will result in the              operations and using ‘semi-
Deep, well-structured soils grow the
                                               degradation of the aquatic/riparian            permanent’ beds
best crops. They are the easiest to
work, so protect them.                                                                        • minimising the use of rotary hoes
                                               While the erosion rate on                      and discs by using tined and non-
The occasional use of gypsum can
                                               permanently grazed pasture has                 inverting implements instead
help to improve the structure of some
                                               been calculated by the DLWC at just
soils, especially sodic clay soils —                                                          • avoiding excessive soil
                                               90 kg per hectare, sloping potato
refer to NSW Agriculture’s Agfact                                                             compaction
                                               land can lose up to a hundred
AC.10 Improving Soil Structure with
                                               tonnes of soil per hectare per crop            • using cover crops and green
                                               through erosion.                               manure crops
Use herbicides as well as cultivation
                                               Paddocks that are not given a spell            • planning crop rotations.
to control weeds. Herbicides are
cheaper than cultivation and help to
preserve soil structure. However, the                                Diagram of a well-structured soil
potency of some residual herbicides
can damage future crops. Learn how                                               Wheel compaction and smearing         Low field variability
                                                                                 confined to narrow strips in some
each herbicide works and how long                                                furrows
its activity persists in the soil (residual                                                                          Soft self-mulching
                                              Well drained surface                                                   seedbed, protected
life) before using it. Keep good                                                                                     by an organic mulch
records of herbicide use.                     High plant
                                              available capacity                                                     Adequate
                                              Neutral pH                                                             permeability/drainage:
Your soil is easily washed or blown           Adequate nutrition                                                     easy root penetration
away through erosion, and its                                                                                        under ridges
                                                 Low–moderate                                                        • closely spaced old
structure is easily damaged by poor              salinity                                                            shrinkage cracks
                                                                                                                     • old root channels
tillage practices such as too many                                                     Minimal water losses
                                                                                                                     and worm holes
                                                                                       through deep drainage
cultivations and by compaction from                                                                                  • small, non-platey
                                                                                                                     subsoil aggregates
farm machinery.                                                                                                      • low sodicity

Aim to maintain, or preferably                 nor cover cropped during the year              Cultivation and machinery
increase, soil organic matter levels           are the most susceptible to erosion.
by substituting organic fertilisers for                                                       Avoid excessive cultivation, which
some of your fertiliser requirements.          Soil management techniques                     wastes money and time and
Also use cover and green manure                                                               damages your soil.
crops, minimise tillage operations             Soil management techniques should
and include pastures in crop                   be used to reduce the risk and                 Minimise the use of rotary hoes. Use
rotations and fallows.                         severity of soil erosion in vegetable          tined and non-inverting implements
                                               production. Adopt an integrated                instead of discs and mouldboard
Erosion control                                package of soil management                     ploughs.
                                               techniques, including:
Soil erosion contributes to:                                                                  Try to get as many crops out of your
                                               • assessing paddocks for erosion               rows or beds as possible before
• loss of fertiliser, soil mineral
                                               risk                                           reworking your paddock.
nutrients, pesticides, seeds and crop

• decline in fertility                         • avoiding steep slopes

• increased production costs.                  • not disturbing natural watercourses

Soil erosion can also result in                • controlling and safely disposing
downstream sedimentation and                   of in-crop surface water
pollution because nutrients and
                                               • diverting external run-off

                                                                                                    BEST SOIL MANAGEMENT PRACTICES

                                                     of soil about the size of a golf ball.
                                                     Try to roll the balls of soil into a
                                                     narrow rod or pencil (3 mm, 1/8”
                                                     diameter). If the soil can be just
                                                     rolled into a crumbly rod it is safe to
                                                     cultivate. If it can easily make a rod
                                                     it is too wet to cultivate. Sand or
                                                     loam soil is too dry to cultivate if a
                                                     rod cannot be rolled, but it is safe to
                                                     cultivate a clay soil in this condition.

Joe Sultana, Freemans Reach. “By keeping my beds                                                Oats as a common winter cover crop — good
I’ve cut the time to prepare a paddock from 7 to 2                                              practice
hours — and the crops are just as good.”
                                                                                                Green manure crops, especially
Keep your cultivation operations                                                                legumes, improve your soil’s
shallow rather than deep, unless                                                                chemical and physical fertility. Be
you have positively identified a                                                                careful not to undo their benefit by
compacted subsoil layer or hard-pan.                                                            ploughing them in too early. For
A hard-pan should be loosened by                                                                maximum benefit green manure
deep ripping when your soil is at the                                                           crops should be worked or used just
right moisture content (see below) to                                                           before they flower.
achieve maximum hard pan
                                                     Cultivate at the right moisture content.

Minimise compaction by keeping                       Cover and green manure
your wheel tracks in the same place.                 crops
Use lighter machinery where
                                                     Cover crops differ from green
                                                     manure crops in that they are not
                                                     grown specifically to be ploughed
Cultivate at the right                               into the soil to add organic matter
moisture content                                     and nutrients. They are more
Cultivating when your soil is too dry                permanent and are slashed, mulched
will make it powdery, will slow water                or sprayed off with a herbicide to
and air movement, and will restrict                  give longer term benefit. Use cover
root growth. Cultivating when it is                  crops, such as oats sown with lupins
too wet will smear (glaze) and                       in winter or millet with cowpeas in
compact your soil, so that water and                 summer, to protect and improve your
air movement and root growth will                    soil’s physical and chemical fertility.
be impeded.                                          Their roots and above-ground growth
                                                     improve your soil’s structure. Cover       Bare soil is easily eroded and damaged by
An easy way to test your soil’s                                                                 raindrops — bad practice.
                                                     crops also protect your soil from run-
suitability for cultivation is to dig a              off and erosion and help the growth
hole to just below the depth of                      of subsequent vegetable crops to be
cultivation and take several samples                 more uniform.


                                                    Further information

                                                    Growers can obtain more
                                                    information about specific aspects of
                                                    better soil management from:

                                                    • NSW Agriculture’s Advisory
                                                    Officer (Vegetable Soil Management)
                                                    at Bathurst on (02) 6333 4377, or
                                                    the local District Soil Conservation
                                                    Officer of the Soil & Vegetation
                                                    Management Directorate of the
                                                    DLWC — refer to the White Pages
                                                    of your local telephone book for
                                                    contact details


                                                    • ‘Soil Sense — Soils Information for
A slashed cover crop using the same beds.
                                                    North Coast Farmers’, from Rebecca
Increase the amount of organic                      Lines-Kelly, Soils Media Officer,
matter in your soil by minimising                   NSW Agriculture, Wollongbar.
cultivation. Organic matter ‘burns up’              Phone (02) 6626 1200.
when it is exposed to the air
by cultivation.

Cover crops improve the soil for following crops.


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