the level of food production. Healthier soils result in higher agricultural productivity,
increased resilience of the land (and soils) to respond to an increasingly challenged
climate and more prosperous communities. Soil can be lost forever due to intense
rainfall when left unprotected or unsupported by appropriate land management
practices. Recognising these challenges, the Queensland Government has been
producing soil management guidelines since 1965 to provide support to farmers
and land managers (Department of Science, Information Technology and Innovation
2015). Early European settlers to Australia had little appreciation of the limitations
particular to the soils and landscape they were developing for agriculture and applied
the farming practices with which they were familiar, those that worked in their
homelands. Much of the cropping was undertaken without recognising the importance of retaining vegetation to conserve the soil and protect biodiversity; land
subdivision was usually based on the simplest geometric, rectangular layout with
little consideration of natural drainage systems, topography and soil types. These
poor land practices were then incentivised by governments who offered incentives
for wholescale clearing and cultivation.
Soil erosion was the first land degradation problem to become readily apparent in
Queensland with cycles of intense and episodic rainfall and the inherent instability of
many soils resulting in a high prevalence to a high risk of erosion (Department of
Science, Information Technology and Innovation 2015). As a result, by 1950, large
areas of cropping land in Queensland had become so badly eroded that they had to be
withdrawn from cultivation. Queensland also has a range of ‘difficult to manage’
soils including acid sulphate soils, sodic soils and salinity. Soil sodicity, for example,
is a natural feature of many Queensland soils, with approximately 45% considered
sodic (Queensland Government 2018c). A common treatment for sodicity in soils is
the use of gypsum to increase the salt content. By raising the level of salts in the soil,
this helps to suppress dispersion. The application rate is typically determined on a
paddock by paddock application given the diversity of soils and cropping systems.
Plants need a steady supply of nutrients from the soil. Required in relatively large
quantities are macronutrients including, but not limited to, nitrogen (N), phosphorus
(P), potassium (K), sulphur (S), calcium (Ca) and magnesium (Mg). Other nutrients
are required in small quantities (micronutrients or trace elements) and include copper
(Cu), zinc (Zn), iron (Fe), manganese (Mn) and boron (B). A shortage or absence of
any one of these essential nutrients can adversely impact plant growth, whilst too
much of any nutrient can also negatively impact plant health. The availability of
nutrients is affected by the pH of the soil. For example, in very acid soils, manganese
and aluminium may be present in toxic concentrations. The amounts of nutrients
available in soils depend on interactions between soil properties from pH to soil type
(clays, sands); soil biology including the organisms living in the soil breaks down
animal and plant matter into nutrient forms that can be used by plants, the volume of
organic matter and soil water. Farmer management of the soils also has an impact,
for example, the use of chemical fertilisers through application of various irrigation
techniques. Declining soil fertility through soil erosion and/or product removal has
created the need for nitrogen addition. Nitrogen fertilisers are a significant expense
for broadacre farmers, so optimising use of fertiliser inputs can reduce this cost, as
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G. Davis
increased resilience of the land (and soils) to respond to an increasingly challenged
climate and more prosperous communities. Soil can be lost forever due to intense
rainfall when left unprotected or unsupported by appropriate land management
practices. Recognising these challenges, the Queensland Government has been
producing soil management guidelines since 1965 to provide support to farmers
and land managers (Department of Science, Information Technology and Innovation
2015). Early European settlers to Australia had little appreciation of the limitations
particular to the soils and landscape they were developing for agriculture and applied
the farming practices with which they were familiar, those that worked in their
homelands. Much of the cropping was undertaken without recognising the importance of retaining vegetation to conserve the soil and protect biodiversity; land
subdivision was usually based on the simplest geometric, rectangular layout with
little consideration of natural drainage systems, topography and soil types. These
poor land practices were then incentivised by governments who offered incentives
for wholescale clearing and cultivation.
Soil erosion was the first land degradation problem to become readily apparent in
Queensland with cycles of intense and episodic rainfall and the inherent instability of
many soils resulting in a high prevalence to a high risk of erosion (Department of
Science, Information Technology and Innovation 2015). As a result, by 1950, large
areas of cropping land in Queensland had become so badly eroded that they had to be
withdrawn from cultivation. Queensland also has a range of ‘difficult to manage’
soils including acid sulphate soils, sodic soils and salinity. Soil sodicity, for example,
is a natural feature of many Queensland soils, with approximately 45% considered
sodic (Queensland Government 2018c). A common treatment for sodicity in soils is
the use of gypsum to increase the salt content. By raising the level of salts in the soil,
this helps to suppress dispersion. The application rate is typically determined on a
paddock by paddock application given the diversity of soils and cropping systems.
Plants need a steady supply of nutrients from the soil. Required in relatively large
quantities are macronutrients including, but not limited to, nitrogen (N), phosphorus
(P), potassium (K), sulphur (S), calcium (Ca) and magnesium (Mg). Other nutrients
are required in small quantities (micronutrients or trace elements) and include copper
(Cu), zinc (Zn), iron (Fe), manganese (Mn) and boron (B). A shortage or absence of
any one of these essential nutrients can adversely impact plant growth, whilst too
much of any nutrient can also negatively impact plant health. The availability of
nutrients is affected by the pH of the soil. For example, in very acid soils, manganese
and aluminium may be present in toxic concentrations. The amounts of nutrients
available in soils depend on interactions between soil properties from pH to soil type
(clays, sands); soil biology including the organisms living in the soil breaks down
animal and plant matter into nutrient forms that can be used by plants, the volume of
organic matter and soil water. Farmer management of the soils also has an impact,
for example, the use of chemical fertilisers through application of various irrigation
techniques. Declining soil fertility through soil erosion and/or product removal has
created the need for nitrogen addition. Nitrogen fertilisers are a significant expense
for broadacre farmers, so optimising use of fertiliser inputs can reduce this cost, as
122
G. Davis