Plant mineral nutrition Flashcards
What are the macronutrients for plants?
Nitrogen, Potassium, Calcium, Magnesium, Phosphorous, Sulfur, Silicon
What are the micronutrients for plants?
Chlorine, iron, Boron, Manganese, Sodium, Zinc, Copper, Nickel, Molybdenum
Where do mobile elements show symptoms first?
Older leaves
Where do immobile elements show symptoms first?
New growth
What is the typical condition of Aussie soils?
- Old
- salty
- acidic
- leached of nutrients
- low in organic matter
Common macronutrient deficiencies of Aus soils?
Nitrogen, potassium, phosphorus (NPK)
+ calcium and magnesium
Common micronutrient deficiencies of Aus soils?
Iron, boron, zinc and molybdenum
What does nitrogen deficiency present as? Treatment?
Yellowing/chlorosis beginning in older leaves.
Organic: any product of a living organism: compost, manure, abattoir waste
Inorganic: urea
What does phosphorus deficiency present as? Treatment?
Dark green/purple malformed leaves with dead spots (necrosis), appearing on older leaves first.
Organic: guano (or chicken manure)
Inorganic: Calcium phosphate
What does Potassium deficiency present as? Treatment?
Mottled or marginal (on the leaf edge) chlorosis/yellowing, occuring in older leaves first. Browning and curling of leaf tips and margins can occur after more time.
Organic: potash (potassium carbonate)
Inorganic: potassium nitrate
What does Calcium deficiency present as? Treatment?
Necrosis on new leaves, root tips, fruit, meristem may die.
Organic: blood & bone, dolomite
Inorganic: Lime
What does Magnesium deficiency present as? Treatment?
Interveinal chlorosis (yellowing) appearing on lower/older leaves first.
Organic: dolomite
Inorganic: Epsom salts
What does Iron deficiency present as? Treatment?
Interveinal chlorosis (yellowing) appearing on younger leaves first.
Organic: Blood and Bone to maintain a prime pH <8
Inorganic: Iron chelate
What does Boron deficiency present as? Treatment?
Typically necrosis/browning in any newly formed organ, appearing on younger leaves and fruits.
Organic: maintain pH < 7
Inorganic: borax
What does Zinc deficiency present as? Treatment?
Chlorosis followed by necrosis, puckered leaf margins and short internodes. Symptoms appear first on younger leaves.
Organic: manure
Inorganic: zinc sulphate
What does Molybdenum deficiency present as? Treatment?
Only a small amount required but some soils are deficient. Displays as interveinal chlorosis and necrosis in older leaves first.
May cause nitrogen deficiency – unable to reduce nitrate to ammonium.
Organic: manure, keep pH > 6
Inorganic: Sodium molybdate
What are the 3 main causes of nutrient deficiency?
- Soil may be naturally low in particular nutrients.
- fertilizer imbalance, e.g. applying only NKP & not replacing other minerals.
- pH, as this affects different nutrient’s solubility
Which charge are soil particles normally?
Negatively charged.
What is Field Capacity?
the level of water that a soil can hold after gravity has assisted drainage.
What is permanent wilting point?
the amount of water remaining in the soil after irreversible wilting occurs.
What is CEC? Cation Exchange Capacity?
Ability of soils to hold and release cations is referred to as cation exchange capacity
One cation is released by exchange for another
Clay soils have small particles with high surface area → high CEC
What are the 3 principal stages of the Nitrogen cycle?
- Ammonification
- Nitrification
- Assimilation
Describe ammonification.
– Majority of soil nitrogen derived from dead organic material
– Soil-dwelling saprophytic bacteria
–Incorporate nitrogen into amino acids and release excess nitrogen in the form of ammonium ions (NH4+)
– In some systems the ammonium ion is not oxidised and can be taken up by the plant
– Otherwise the ammonium ion is converted to nitrate by nitrification
Describe Nitrification.
The oxidation of ammonia or ammonium ions
Performed by soil bacteria and is an energy yielding process allowing the reduction of carbon dioxide (similar to the use of light in photosynthesis)
What is dentrification?
Nitrate is reduced to volatile forms of nitrogen such as nitrous oxide.
Occurs more in waterlogged soils as driven by anaerobic conditions.
How does Nitrogen get fixed by biological processes?
Symbiotic bacteria such as rhizobia on legumes are nitrogen fixing with plant roots.
Free-living bacteria such as cyanobacteria can also perform this.
How is Nitrogen transported around the plant?
As amino acids in phloem.
What are the sources of sulphur?
Weathered rocks
Volcanic or fossil fuels release
Rain in areas with high atmospheric sulphur dioxide
What three criteria define an essential nutrient/element for a plant?
- Required for a plant to complete life cycle
- Clear physiological role
- Plants display a clear symptom if deficient
