1.1 Properties of a ‘Healthy’ Soil
Friability (tilth)
A ‘perfect’ agricultural soil will form small (2-3mm)
aggregates that do not disintegrate under heavy rain or tillage, but have
sufficient pore spaces to hold water. Ideally, the aggregates should bond
together slightly to prevent them from moving down the slope with water
flows, but break apart easily when cultivated.
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Allow water and air to move more freely in the soil.
As water infiltration improves, waterlogging problems decrease and
better use is made of soil water.
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Are easily worked improving seed and soil contact and
allow uniform germination and emergence of seedlings.
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Allow roots to penetrate and better exploit water and
nutrients in the soil.
Freedom from Barriers
Barriers to roots, that limit their growth and ability to
exploit the soil, prevent crops achieving potential yields. Barriers to
root growth, such as a compacted layer, can be reduced or eliminated.
Those from boron, shale and stone or high lime layers are difficult or
expensive to change. The productive potential of a paddock with such
barriers will be much less than the rainfall potential.
Provides Storage for Water and Nutrients
The capacity of the soil to hold water and its
availability to plants directly affects productive potential. The ability
of a soil to store water and nutrients depends on the number and size of
pores, ‘storage sites’ in the soil and the amount of clay and organic
matter in a soil. Measuring the ‘cation exchange capacity’ of the soil
can assess the storage capacity for a range of nutrients. The availability
of nutrients from this store can be assessed by standard soil and tissue
tests.
Resistance to Erosion by Water and Wind
Exposed soils with poor structure and lack of organic
matter or vegetative cover are prone to erosion.
Biologically Active
Soil organisms carry out a wide range of processes
that are important for soil health and fertility. There is a two-way
relationship between soil organisms and agricultural production. The
retention of plant residues provides an important source of energy and
nutrients for soil organisms. In turn, they improve organic matter
breakdown, nutrient availability, soil structure, disease suppression and
the degradation of pollutants such as herbicide residues.
Freedom from Pests and Diseases
Root, stem and leaf pests and diseases can be
carried in the soil. Root disease control, combined with improved soil
structure that has allowed better root exploitation of the soil, has been
one of the main reasons for yield increases in many areas during the last
decade.
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How ‘healthy’ is your soil?
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What is limiting the productive potential of your
soil?
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Are there opportunities to improve your soil
‘health’?
1.1 Properties of a ‘Healthy’ Soil
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