Phosphorus

Question 1

Phosphorus cycle

Answer 1

P in oceans then enters rock
Released into soil through weathering
Moves through plants and animals
Can be taken up by microbes
Or surface runoff and then back to oceans
New rock formed at bottom of ocean
Agriculture = high extraction, rapid runoff and slow recycling
Little free phosphate

Question 2

Phosphorus pools

Answer 2

Labile (bioavailable) - simple form; highly reactive so can form phosphate and collate to minerals and metals; inorganic so available to plants
Complexed inorg P - insoluble?
Organic P - made through biological processes; immobile so unavailable (immobilisation of labile form)

Question 3

Orthophosphate

Answer 3

Common labile form of P
Very little of it and very reactive
Hard for plants to access so transformations needed
Some soils have higher orth
When used up, rhizosphere low in labile P and phosphate can be immobilised so needs to be converted back to labile P
MC and microbes can help remineralise

Question 4

Limited P

Answer 4

P can be limited which impacts crop growth and yields
Lots of fertiliser applied to avoid this
P is often in unavailable form

Question 5

Global reserves

Answer 5

Finite resource - excess in some regions, little in others
Precious resource
Can lead to eutrophication in some areas

Question 6

Solutions to P limitations

Answer 6

Direct - improve plant efficiency; less reliance on rock phosphate
Indirect - crop resistance to stress; better P recovery; better animal P use efficiency

Question 7

Plant microbiome

Answer 7

Phyllosphere - microbes on plant leaves
Root endosphere - inside plant roots
Rhizosphere - zone in soil around roots; high nutrients
Rhizoplane - surface of root cells
Myccorrhizosphere - MC fungi

Question 8

Microbe importance

Answer 8

Greenhouse gas emissions
Plant growth promotion (inc. auxin production for root growth)
Plant pathogens
Pathogen supression
Nutrient acquisition
Bioremediation

Question 9

DNA sequencing

Answer 9

Extract DNA from microbial community
Amplicon sequencing - target 1 gene of interest and PCR
Metagenomes - short fragments from all DNA
Community gene expression - sequence RNA and proteins; huge diversity and see functioning?

Question 10

Biotech solutions

Answer 10

Transgenic plants
Engineer microbes/microbiome
Microbial innoculants
Designer rhizosphere

Question 11

Phosphonates

Answer 11

Abundant in plant tissue
Phosphatase not strong enough to break it down - glyphosate is stronger
Can get microbial phosphatases