Phosphorus

Question 1

How is Phosphorous taken up by the plant?

Answer 1

An Anion

Question 2

What is the essential function of Phosphorous in plants?

Answer 2

1. P is an essential constituent of ATP which traps and moves energy for different functions.
2. Used in phospholipids in cell membranes
3. Used in Nucleic acids

Question 3

True or False, The ionic species of the soils solution vary with pH?

Answer 3

True

Question 4

At a pH of 5 90% exists as …

Answer 4

H₂PO₄ (-)

Dihydrogenphosphate-

Question 5

At a pH of 7 H2PO4 (-) dissociates to what?

Answer 5

HPO₄^2-

Hydrogenphosphate

In this state, the two forms are similar in quantities.

Question 6

Why does the amount of P in the soil solution tend to be low?

Answer 6

Because P tends to precipitate in soil forms even in well-fertilised soils.

Question 7

What makes grasses good scavengers of P despite its low % in soil solution?

Answer 7

1. High rooting densities.
2. Infection of endotrophic mycorrhiza whos hyphae ramify within the soil and contribute to root exploration.

Question 8

Reserves of P exist in both organic and inorganic forms?

True or False

Answer 8

True

Question 9

In semi maintained areas with little or no fertiliser input, organic reserves account for around 75% of P reserves.

What will determine its subsequent availability to grasses?

Answer 9

Rate of mineralisation by microbes.

Therefore factors including temperature, pH, aeration and soil texture will affect the rate of mineralisation.