LO 5.4 - Controlled & Slow release fertilisers

Question 1

Question

What are Slow release fertilisers?

Slow release and Controlled fertilisers

Answer 1

Slow release fertilisers
* Contain elements that are not immediately available to plants.

or

• Contain additive that inhibits the rate of nutrient release.

Phosphate must be dissolved by acids to become water soluble.

Slow release and Controlled fertilisers

Question 2

Question

Where are Slow release fertilisers (SRFs) commonly used?

Slow release and Controlled fertilisers

Answer 2

Slow release fertilisers
SRFs often used in field veg production.

Difficult to predict rate of release - depends on temp, moisture, pH.

Slow release and Controlled fertilisers

Question 3

Question

What are Controlled release fertilisers (CRFs)?

Slow release and Controlled fertilisers

Answer 3

Controlled release fertilisers
* Encased in a resin coating which allows them to release over a period of time.
* Release over different timescales, 3-4 months, 8-9 months, 12-14 months.
* Controlled by the thickness of the coating and the size/number of pores.

Sometimes called ‘smart release’ fertilisers

Slow release and Controlled fertilisers

Question 4

Question

How do CRFs work?

Slow release and Controlled fertilisers

Answer 4

Controlled release fertilisers
* Temperature of growing medium, based on 21 degrees.
* CRFs can be incorporated into the compost prior to potting, or plants can be ‘topdressed’.
* CRFs also used in landscape maintenance and turfgrass.

Examples include Osmocote, Multicote, Sierrablen.

Slow release and Controlled fertilisers