There are three major study groups across Australia's Norhteastern Rangelands: non-calcic brown soils, red, yellow and grey earths na dgre, brown and red clays, THey are now classified as red chromosols, red, yellow & grey kandosols and Grey& brown vertosols.
Red chromsols.
These soils have non-calcarous profiles. The topsoils are well differentiated from subsoil horzons, they have an abrupt texture increase from topsoil to subsoil. THe massive topsoils are over strongly structured subsoils. They contain minerals such as quartz, kaolin, iron and aluminium oxides and oxyhydroxides. They have a neutral pH, have a moderate cation exchange capacity and low-moderate natural fertility.
red, yellow and grey kandosols
these soils have non-calcareous profiles, have weakly differentiated soil horizons with usually gradational texture changes down soil profiles, they have a stable, massive structure and earth fabric. They contain the same minerals as the chromosols and hvae a weakly acidic-neutral pH with low cation exchange capacity and low natural fertility.
vertosols
these soils have a uniform clay texture down the soil rofiles and are very strongly structured with weakly differentiated soil horizons. They have a very strong swell-shrink on wetting and drying. They contain smectitic clay, illitic clay and quartz. these soils have a neutral-alkaline pH with calcareous and gypseous profiles and moderate to high cation exchange capacity and moderate to high fertility.
Swell Shrink behaviour
when the soils are wet, the crystal lattices of smectitic clays expand and when they dry out they lose water returning the crystal lattices to their original sizes.
development of gilgai microrelief
topsoil falls down cracks in the dry season causing partial inversion of the soil profile. Rainwater enters the profile in the wet season, resulting in swelling, closing the cracks, exerting stress and lateral and upward expansion of the soil. Subsoils commonly alkaline and with lime nodules, are pushed up into 'puffs' forming gilgai microrelief. Gilgai depressions hold water after rain.
Soil requirements for Pasture growth
Good pasture growth depends on availability of solar radiation, water, air, anchor for roots and a good supply of essential plant nutrients.
Nutrient uptake through rot hairs
Nutrient elements are taken up through the root hairs in a soluble form from the soil solution. Tiny delicate root hairs, each actually a single cell and growing at right angles to the root, absorb moisture and the dissolved nutrients from the soil solution. There are 17 elements that are essnetial for growth of all plants. Macronutrients are ones needed in large amounts suchas H, C, O, N, P, K. Ca, Mg, S and micronutrients (trace elements) are needed in minor amounts such as Cl, Fe, B, Mn, Zn, Cu, Ni, Mo. Elements important to some plants include Na, Co and Si whereas Aluminium and other heavy etals are undesirable for all plants.
Law of the Mimimum
Plant nutrients are limited in teh deficient zone where plant yeild increases with increasing nutrient concentration and in the adeuqte zone palteau growth is sustained but not enhance by increasing nutrient supply. Law of the minimum suggest that ' the level of plant production can be no greater than that allowed by the most limiting of the essential plant growth factors. '
Nutrient Deficiencies in the Northeastern Rangeland Soils
Element deficiencies requiring correction include nitrogen,phosphorous and sulphur. Nitrogen is grossly deficient in most UAstralian SOils and can b replaced int eh oil by adding fertiliser, growing elgumes and/or incorportaing organic matter (manure) into the soil, or direct protein supplementation into animals. Phosphorous is deficient or grossly deficient in many Australian soils and is often replaced by fertilisers however direct supplementation can be give to animals through blended feeds and licks. Sulphur is deficient in basaltic terrains in the northeastern rangelands and requires direct supplementation into animals through blended feeds and licks
Botulism can occur when cattle eat hay or silage polluted by carcass material or bones when grazing, or poultry litter. THis will happen whne there is a lack of feed or a phosphorous deficiency in the feed. The disease causes paralysis and teh animal usually dies with treatment only possible in the early stages and requires an antitoxon. Cattle grazing on phosphorous deficent soils tend to develop a peg-leg gait and satisfy their craving for phosphoous by bone chewing. Botulism is caused by a neurotoxin secretd by the bacterium clostridium botulinum. It belongs to a group of organisms that produce food poisoning, tetanus, gas gangrene, pulpy kidney, black leg and would infections. THe anaerobic bacterium thrivse in decaying animal and platn material under warm, moist conditions. Prevention involves vaccination and good nutrition during the dry season. All carcasses, bones or decaying material should be burnt or buried.
Supplying Nutrients to Pasture Plants
The availability f elements int eh soil to plants depends on teh amount of the element present in the soil, the rate of release from mineral or organic material and the form of the element in teh soil as well as soil chemical processes.
Soil Colloids
Colloids are all soil particles finer than 0.002mm. Colloidal organic particles are known as humus and colloidal mineral particles are known as clay. The sheet-like silicate minerals produced by weathering of rock forming minerals are known as clay minerals. Colloids present enormous amounts of reactive particle surfaces in the soils.
Clay minerals re sheet-like, phyllosilicates. Much of the surface area of the inorganic colloids is on internal surfaces, like the urface area presented by the pages of a partly-opened book.
Processes ont ehs urfaces of the tiny soil coloids control the ability of soils to supply nutrients air and water to plant roots. responses of soils to cultivation, absorption of pesticides and other pollutants in soils, erosion processes at the soil-water interface, engineering stability of subsoil structures and shrink-swell properties of soils.
Exchangeable Cations in the Soil
Nutrients supply as hydrated cations or anions in the water. These ions are relased from organic matter by microbial decomposition, mineral grains or fertilisers by weathering or dissociation of water molecules. Nutrient ions are held in teh soil solution, on surfaces of fine mineral particles and on surfaces of fine particles of organic matter.
Int he soil, fine particles of inorganic minerals and of organic matter generally carry a net negative charge and attract nutrient cations (however this is not necessarily the case in many of the highly weathered, acidic, iron-rich, soils of the humid tropics).
Negative charges on the surfaces of clays and organic colloids attract the cations in the soil solution. Electrical neutrality is preserved by cations held loosely on teh surface of the colloid, forming a diffuse double layerof electrical charge. Cations on teh particle surface often swap places with other cations in thesoil solution. The Cation Exchage Capacity (CEC) is the capacity of a soil to hold cations on colloid surfaces and to supply thosenutrient cations ot soil solution for uptake by growing plants. CEC is an important measure of soil fertility.
Where ther is adequate water present, in diffuse double layers trivalent and bivalent cations are held mroe srongly than monovalent cations and smaller cations are held more strongly than large ones. Electrical neutrality in the difuse double layer is maintained by positive charge from teh number of monovalent cations needed to balance negative charges on colloid surface, the number of bivalent cations needed or the number of trivalent cations needed.
Monovalent cations will be more numerous and will occupy mroe space in teh diffuse double layer, than any bivalent or trivalent cations in teh soil solution.
Sodium Dominated soils (dispersion)
Sodium ions are monovalent with large radius and large hydration shels. Numerous sodium ions are wekaly held on colloid suraces. Wide difuse double layers prevent sodium-saturated colloids coming close together. COlloidal particles are pushed too far apart for electrotatic forces to lock them together. Slaking occurs when COlloids are held apart wit larger, sawdust-like particles and dispersion occurs when colloids are held apart with very fine, smoke-like particles.
Calcium Dominated soils (aggregation)
Calicium-saturated colloids have htin diffuse double layers. Calcium colloids approach one another closely and by electrostatic attraction, form stable aggregates. Colloidal particles in suspension flocculation and in soils aggregate.
Learn More
PED Talk: Soil: Texture, Clay and Cation Exchange
Red chromsols.
These soils have non-calcarous profiles. The topsoils are well differentiated from subsoil horzons, they have an abrupt texture increase from topsoil to subsoil. THe massive topsoils are over strongly structured subsoils. They contain minerals such as quartz, kaolin, iron and aluminium oxides and oxyhydroxides. They have a neutral pH, have a moderate cation exchange capacity and low-moderate natural fertility.
red, yellow and grey kandosols
these soils have non-calcareous profiles, have weakly differentiated soil horizons with usually gradational texture changes down soil profiles, they have a stable, massive structure and earth fabric. They contain the same minerals as the chromosols and hvae a weakly acidic-neutral pH with low cation exchange capacity and low natural fertility.
vertosols
these soils have a uniform clay texture down the soil rofiles and are very strongly structured with weakly differentiated soil horizons. They have a very strong swell-shrink on wetting and drying. They contain smectitic clay, illitic clay and quartz. these soils have a neutral-alkaline pH with calcareous and gypseous profiles and moderate to high cation exchange capacity and moderate to high fertility.
Swell Shrink behaviour
when the soils are wet, the crystal lattices of smectitic clays expand and when they dry out they lose water returning the crystal lattices to their original sizes.
development of gilgai microrelief
topsoil falls down cracks in the dry season causing partial inversion of the soil profile. Rainwater enters the profile in the wet season, resulting in swelling, closing the cracks, exerting stress and lateral and upward expansion of the soil. Subsoils commonly alkaline and with lime nodules, are pushed up into 'puffs' forming gilgai microrelief. Gilgai depressions hold water after rain.
Soil requirements for Pasture growth
Good pasture growth depends on availability of solar radiation, water, air, anchor for roots and a good supply of essential plant nutrients.
Nutrient uptake through rot hairs
Nutrient elements are taken up through the root hairs in a soluble form from the soil solution. Tiny delicate root hairs, each actually a single cell and growing at right angles to the root, absorb moisture and the dissolved nutrients from the soil solution. There are 17 elements that are essnetial for growth of all plants. Macronutrients are ones needed in large amounts suchas H, C, O, N, P, K. Ca, Mg, S and micronutrients (trace elements) are needed in minor amounts such as Cl, Fe, B, Mn, Zn, Cu, Ni, Mo. Elements important to some plants include Na, Co and Si whereas Aluminium and other heavy etals are undesirable for all plants.
Law of the Mimimum
Plant nutrients are limited in teh deficient zone where plant yeild increases with increasing nutrient concentration and in the adeuqte zone palteau growth is sustained but not enhance by increasing nutrient supply. Law of the minimum suggest that ' the level of plant production can be no greater than that allowed by the most limiting of the essential plant growth factors. '
Nutrient Deficiencies in the Northeastern Rangeland Soils
Element deficiencies requiring correction include nitrogen,phosphorous and sulphur. Nitrogen is grossly deficient in most UAstralian SOils and can b replaced int eh oil by adding fertiliser, growing elgumes and/or incorportaing organic matter (manure) into the soil, or direct protein supplementation into animals. Phosphorous is deficient or grossly deficient in many Australian soils and is often replaced by fertilisers however direct supplementation can be give to animals through blended feeds and licks. Sulphur is deficient in basaltic terrains in the northeastern rangelands and requires direct supplementation into animals through blended feeds and licks
Botulism can occur when cattle eat hay or silage polluted by carcass material or bones when grazing, or poultry litter. THis will happen whne there is a lack of feed or a phosphorous deficiency in the feed. The disease causes paralysis and teh animal usually dies with treatment only possible in the early stages and requires an antitoxon. Cattle grazing on phosphorous deficent soils tend to develop a peg-leg gait and satisfy their craving for phosphoous by bone chewing. Botulism is caused by a neurotoxin secretd by the bacterium clostridium botulinum. It belongs to a group of organisms that produce food poisoning, tetanus, gas gangrene, pulpy kidney, black leg and would infections. THe anaerobic bacterium thrivse in decaying animal and platn material under warm, moist conditions. Prevention involves vaccination and good nutrition during the dry season. All carcasses, bones or decaying material should be burnt or buried.
Supplying Nutrients to Pasture Plants
The availability f elements int eh soil to plants depends on teh amount of the element present in the soil, the rate of release from mineral or organic material and the form of the element in teh soil as well as soil chemical processes.
Soil Colloids
Colloids are all soil particles finer than 0.002mm. Colloidal organic particles are known as humus and colloidal mineral particles are known as clay. The sheet-like silicate minerals produced by weathering of rock forming minerals are known as clay minerals. Colloids present enormous amounts of reactive particle surfaces in the soils.
Clay minerals re sheet-like, phyllosilicates. Much of the surface area of the inorganic colloids is on internal surfaces, like the urface area presented by the pages of a partly-opened book.
Processes ont ehs urfaces of the tiny soil coloids control the ability of soils to supply nutrients air and water to plant roots. responses of soils to cultivation, absorption of pesticides and other pollutants in soils, erosion processes at the soil-water interface, engineering stability of subsoil structures and shrink-swell properties of soils.
Exchangeable Cations in the Soil
Nutrients supply as hydrated cations or anions in the water. These ions are relased from organic matter by microbial decomposition, mineral grains or fertilisers by weathering or dissociation of water molecules. Nutrient ions are held in teh soil solution, on surfaces of fine mineral particles and on surfaces of fine particles of organic matter.
Int he soil, fine particles of inorganic minerals and of organic matter generally carry a net negative charge and attract nutrient cations (however this is not necessarily the case in many of the highly weathered, acidic, iron-rich, soils of the humid tropics).
Negative charges on the surfaces of clays and organic colloids attract the cations in the soil solution. Electrical neutrality is preserved by cations held loosely on teh surface of the colloid, forming a diffuse double layerof electrical charge. Cations on teh particle surface often swap places with other cations in thesoil solution. The Cation Exchage Capacity (CEC) is the capacity of a soil to hold cations on colloid surfaces and to supply thosenutrient cations ot soil solution for uptake by growing plants. CEC is an important measure of soil fertility.
Where ther is adequate water present, in diffuse double layers trivalent and bivalent cations are held mroe srongly than monovalent cations and smaller cations are held more strongly than large ones. Electrical neutrality in the difuse double layer is maintained by positive charge from teh number of monovalent cations needed to balance negative charges on colloid surface, the number of bivalent cations needed or the number of trivalent cations needed.
Monovalent cations will be more numerous and will occupy mroe space in teh diffuse double layer, than any bivalent or trivalent cations in teh soil solution.
Sodium Dominated soils (dispersion)
Sodium ions are monovalent with large radius and large hydration shels. Numerous sodium ions are wekaly held on colloid suraces. Wide difuse double layers prevent sodium-saturated colloids coming close together. COlloidal particles are pushed too far apart for electrotatic forces to lock them together. Slaking occurs when COlloids are held apart wit larger, sawdust-like particles and dispersion occurs when colloids are held apart with very fine, smoke-like particles.
Calcium Dominated soils (aggregation)
Calicium-saturated colloids have htin diffuse double layers. Calcium colloids approach one another closely and by electrostatic attraction, form stable aggregates. Colloidal particles in suspension flocculation and in soils aggregate.
Learn More
PED Talk: Soil: Texture, Clay and Cation Exchange