soil and pasture Flashcards
What are the three major components of soil
Sand, silt, clay
What is the properties of clay
clay is the most fertile, the higher the clay content in soil, the more fertile it is, also more prone to waterlogging
How is soil texture being determined
By the percentage of component of each of the three components of soil.
How does soil texture determines the feel and physical properties of soil
- storage of air and water
- the movement and availability of water and nutrients
- organic matter level
- ease of root growth
- workability and resistance to erosion
What are the percentage of clay in soil and the corresponding name
<10% clay: sands 10-20% clay: sandy loam 20-35% clay: clay loam >35% clay: clays >60% clay: heavy clays
what are the three main layers in the soil profile and their explanations
Top soil(A horizon): most important, the layer being cultivated, contain most of the nutrients available to plants. Sub soil(B horizons): Receive materials leached from A horizon. Depth and water holding capacity of the B horizon greatly affect value of soil. Parent material(C horizon): If soil is shallow and parent material is rock, plant roots can not penetrate, restricting growth.
What are the colours of the soils and their corresponding explanation
Organic matter:
dark brown soil indicates organic matter, well drainage good structure, high nutrients level. black indicate high sodium level and water drainage.
Mineral matter:
red orange: iron oxide good drainage, aerobic low leaching.
green/ grey/ blue: water logged.
dull yellow: seasonal water logging, anaerobic condition, high level of lime.
what is the cause of water repellency and how it can be solved
hydrophobic organic matter produced by decomposition of plants, causing patchy germination increasing the risk of erosion. Can be solved by adding clay into the soil.
What are the consequences of water logging?
It cause oxygen deficiency in roots, accumulating toxins, decrease root growth and survival.
Causes of soil acidity and how to solve
Inefficient use of nitrogen fertilizers, leaching of nitrates, removal of plants cause aluminium in soil to become soluble and retard root growth, decrease nutrients availability and lower microbial activity in rhizobia.
Application of lime to lower soil acidity.
Causes of soil salinity and how to solve
- Salt are brought by wind from sea by wind and rainfall, accumulated in clay-sub soils. Widespread clearing, use of shallow rooted vegetation increase recharge to ground water.
- Increase water use by planting deep rooted perennials, protect remain vegetation, plant trees on recharge zones, use salt tolerance perennials.
What does CEC stand for in a soil?
- Cation exchange capability
- Complex engineered cohesion
- Chemical excretion of carbon
- Cation exchange capacity
- Clean energy capability
- Cation exchange capacity
What is the explanation of CEC
the ability of soil to hold onto nutrients, varies with pH, the higher the percentage of clay in soil the higher the CEC, acts as buffer to soil acidification.
Which one of the following is most likely to be associated with a brown to black colour in soil?
- Granite parent rock
- Waterlogging
- Organic matter
- Limestone derivation
- High iron levels
- Organic matter
What are the three pasture system
Permanent pasture, phase farming, ley farming
The pasture system in higher rainfall area
tends to be permanent or semi-permanent, all year pasture.
The pasture system in drier mixed farming region
ley pasture phase, rely on self-regeneration of legume (subterranean clover, annual medics)
Characteristics of phase farming
Due to delayed cycle, subterranean clover are unable to regenerate from the hard seed remain dormant during the crop stage, can re-sow wide range of pasture species. Not expect to self-generate is re-seeded.
Temperate perennial zones, location and characteristics
South eastern coastal areas including west of Tasmania. In this zone pastures includes perennial ryegrass and white clover, they are high production, well adapted to grazing but restricted to high rainfall coastal area. They have high nutritive values and are important to dairy industry.
Temperate perennial grass annual legume zone location and characteristics
south west(Perth) and south east near coastal area also east coastal Tasmania. Phalaris(more drought resistance) the most drought tolerant temperate grass sown in Aus, usually with subterranean clover
Lucerne area location and characteristics
same as the temperate perennial grass and annual legume zone.
Lucerne is a deep-rooted perennial legume adapted to several zones, on suitable soils rainfall exceeds 400mm. Mixture with other grasses and annual legumes, sensitive to acid soils and water logging
Mediterranean annual pasture zone location and characteristics
On top of the temperate perennial grass and annual legume pasture zone.
Subclover and annual medics have been basis for the legume ley pasture system in the wheat belt on suitable soils annual legume persist >350mm in southern Aus. Subclover suited to well drained acid sandy loam soils and medics prefer clay loams and pH>6.5
Which pasture zone is dominant in Tasmania and along the south-east coast of Australia?
a) Humid coastal perennial zone
b) Lucerne pasture zone
c) Temperate perennial pasture zone
d) Temperate perennial grass – annual legume zone
e) White clover pasture zone
d) Temperate perennial grass – annual legume zone
Grass growth habits: what three types of growth, two types of chromosome numbers and their characteristics
- bunch type (caespitose) tillers
- stoloniferous: stolon trail on soil surface, normal leaves
- rhizomatous: grow beneath soil surface, white leaves
Most grasses are diploid, tetraploid ryegrass have 4 sets of chromosome, they have larger cell size, larger leaves fewer tillers more soluble carbohydrates and greater intake by ruminants
C3 grasses characteristics
grows in cool areas. lower production comparing with C4. Less water efficient
chloroplasts in mesophyll cells of leaves. CO2 is fixed to RuBP in reaction catalysed by rubisco, 3C is re-arranged for synthesis of carbohydrates and new RuBP however it also oxygenates RuBP to CO2 by photorespiration in high temperature and light intensity.
C4 grasses characteristics
grows in warm areas. higher production more water effective.
carbon fixation and carbohydrate synthesis occurs in different cells. mesophyll chloroplasts produce energy but absent of Rubisco, CO2 is fixed as 4C transferred to bundle sheath cells where CO2 is concentrated, avoid photorespiration. additional steps requires more ATP but more efficient fixing carbon in drought, no need stromates wide open
Which ONE of the following BEST describes the properties of C3 grasses relative to C4 grasses?
a) Grow best at higher temperatures, higher water efficiency
b) Grow better at lower temperatures, higher lignin formation
c) Grow better at lower temperatures, lower production
d) Grow better at higher temperatures, greater production
e) Similar optimum growing temperatures, greater production
c)Grow better at lower temperatures, lower production
Grass seed(caryopsis) content
Monocotyledon, consists of endosperm and an embryo, embryo consists of a primary shoot and root and scutellum.
Process of grass germination
uptake of water by the seed stimulate respiration, cell division and secretion of enzymes, break down starch in the endosperm into sugar, sugar pass to embryo to support growth of primary root and shoot.
Process of grass leaf and tiller formation
leaves develop from the apical dome(meristem) at the base of the stem (below grazing level)
Process of leaf growth
Most grasses produce tillers which are connected to each other. The number of leaves per tiller remains constant through out life. Reproductive growth is stimulated by day length and temperature.
Which ONE of the following is NOT correct about the germination and growth of grasses?
a) Grass seed is a fruit called caryopsis? and consists of an endosperm and an embryo
b) Leaves grow from the apical dome(apical meristem) at the base of the stem
c) Most grasses produce tillers which are all connected to each other
d) The number of leaves per tiller remains constant throughout life of plant
e) Reproductive growth is stimulated by more intensive defoliation
e)Reproductive growth is stimulated by more intensive defoliation
Legume seed content
Dicotyledon, two cotyledon enclose the embryo, no endosperm, cotyledons serve as energy source for embryo
Mechanisms for hardseededness in legume
Seed dormancy allow formation of a persistent seed bank, impermeable layer in the seed coat prevents water uptake and germination to prevent false break germination. The rate of breakdown is temperature dependent, varies between species. Hard seed is important in rotation with crops(ley pasture system)
Legume seed germination process
Seed imbibes water causing the growth of tap root and then secondary root, cotyledons pulled over soil surface, emergence of unifoliate leaf then trifoliate leaf.Main stem elongates and a leaf is produced at nodes. Axillary buds at the cotyledonary node form new shoots or branches.
Chopping off the growing point will not kill the legume but encourage it to branch (become denser).
Reproductive growth of legume
Influenced by temperature and photoperiod, inflorescence arise from bud at shoot apex of leaf apex
In relation to hardseededness as a mechanism of seed dormancy, which of the following is FALSE?
a) Hardseedednessis common in legumes
b) Due to their level of hard seed breakdown, subterranean clover is well suited to phase pastures
c) Short ley pastures require a high proportion of hard seed and medics are therefore ideal in this type of pasture system
d) Breakdown of the seed coat is temperature dependent
e) Hard seed break down varies between species and cultivars
b)Due to their level of hard seed breakdown, subterranean clover is well suited to phase pastures
not suitable for phase farming as the hard seed are not expected to re-generate but is re-seeded after cropping stage
What are the two forms of carbon in plants
Structual carbohydrates: cellulose, hemi-cellulose, lignin
Non-structual carbohydrates: water soluble carbohydrates
The light dependent reaction in photosynthesis
absorbing energy from sunlight by chlorophyll to oxidise water and produce oxygen and energy (ATP and NADPH)
The light independent reaction in photosynthesis
Carbon fixation using energy from light reactions to produce carbohydrates (clavin cycle)
How will photosynthesis increases given at optimum temperature (25 degree celsius) and optimum levels of avaliable water
Increases at high light intensity and increases with CO2 conc.
What is LAI
Leaf Area Index, the surface area of leaves per unit of ground area, the LAI at which virtually all the light is intercepted is usually in the range from 4 to 6 for grasses.
What is pasture growth determined by
- efficiency of the photosynthetic process
2. amount of light intercepted by leaves
Impact of grazing on pasture growth depend on
time of grazing
frequency of grazing
intensity of grazing
Which stage should perennial ryegrass be grazed and why
At the 3 leaf stage as grazing too soon cause loss of growth and too late reduce the amount of leaf consumed by animals. the water soluble carbohydrate is highest in 3 leaf stage.
Why some pasture don’t need to be rested what are they
subclover and broad leaf weeds. they maintain some leaf area for photosynthesis even grazed low to the ground and can therefore tolerate countinous grazing
Which ONE of the following is TRUE for perennial rye grass?
a) If grazed at a 2 leaf stage, the re-growth potential of perennial rye grass is at optimum
b) Water soluble carbohydrates are lowest at the 3 leaf stage
c) Grazing of perennial rye grass should begin at the 3-leaf stage
d) Grazing of perennial rye grass should begin at the 4-leaf stage
e) Water soluble carbohydrates are concentrated in the dying leaf due to absence of respiration
c)Grazing of perennial rye grass should begin at the 3-leaf stage
What are animal impacts on pasture
defoliation: leaf area and growth, selective grazing
treading/ trampling: direct effect on plant’s leaves and growing points, coil compaction, pugging.
Provide nutrients in dung and urine
Protein benchmarks for rumens
Rumen micro-organisms need protein (minimum 7%) to digest cellulose. Green pastures high in protein (grasses 15% and legume 25%)but dry feed can drop to 5% in summer.
Sheep and cows may only need 7-8% protein dry, 8-10% in late pregnancy and 12-14% while lactation. Growing labs requires 12-16%.
Three types of grazing management
Set stocking: continuous grazing in most paddocks， some are rested seasonally
Rotational grazing: rotated between paddocks, each is grazed and rested, determined by pasture growth and availability, promote ultilization.
cell grazing: high intensity rotational grazing system with large number of paddocks and short grazing intervals
three common livestock health risk associated with grazing pastures
Grass tetany: low magnesium in blood due to low levels of magnesium in green pastures/ cereal crops
Hypocalcaemia: low calcium in winter cereals, late pregnancy and lactation.
white muscle disease: low selenium/ vitamin E in dry pastures during summer and autumn
6 anti-nutritional factors in pastures
- Fungal and bacterial alkaloids (temperate grasses)
- Oestrogenic compounds (clovers)
- Photosensitising agents
- Bloat and red-gut
- Nitrate poisoning
- Mineral deficiencies
5 factors neurological disorders associated :
- Phalaris staggers
- Perennial ryegrass staggers, tall-fescue toxicosis (fungal endophytes)
- Paspalam staggers
- Annual ryegrass toxicity (bacterial toxin)
- Lupinosis (fungal toxin)
3 metabolic disorder
Bloat: natural foaming agents in legumes and some rapidly growing grasses cause a stable foam to form in the rumen prevent animals from belching.
Red-gut: inflammation and twisting of the intestine resulting from grazing pure legume pastures.
Nitrate poisoning: excessive nitrates in certain pasture cause scouring and sudden death from nitrites in blood.
Photosensitivity
Dermatitis and conjunctivitis after exposure to sunlight
Ingestion of photodynamic chemicals
Liver damage and accumulation of phylloerythrin from breakdown of chlorophyll
Phyto-oestrogens:
Many subterranean clover varieties and other clovers, such as red clover, contain high levels of the phytooestrogens.
These compounds permanantly impair the fertility of the ewes and to a lesser extent cattle.
Short-term effects can include a prolapsed uterus, difficult lambing and a declining lambing percentage.
what are the macronutrients
Macronutrients (primary)
Nitrogen
Phosphorus
Potassium
Macronutrients (secondary and tertiary)
Sulfur
Calcium
Magnesium
Which one of the following elements is classed as a secondarymacronutrient essential for growth of pasture plants?
- Copper
- Zinc
- Molybdenum
- Magnesium
- Manganese
- Magnesium
Short answer questions Soil salinity is a major threat to Australian agriculture. Briefly outline the causes or process of how soils become saline (1 mark), and suitable management options to halt this increase (1 mark).
- Salt are brought by wind from sea by wind and rainfall, accumulated in clay-sub soils. Widespread clearing, use of shallow rooted vegetation increase recharge to ground water.
- Increase water use by planting deep rooted perennials, protect remain vegetation, plant trees on recharge zones, use salt tolerance perennials.
Provide four examples of how soils, pastures or animals may be influenced by set stocking compared to rotational grazing (2 marks)?
- Set stocking cause more uneven grazing
- Rational grazing ultilise pasture that are neglected by animals in set stocking.
- In rotational grazing cause a decline in pasture quality and decrease in proportion of clover comparing with set stocking.
- Rational grazing can manage animal health problems by introducing pasture with lower worm burden after drenching.
