1. RHS Level 2
Certificate
Year 2 Week 8 – fertilizers and
alternative growing media.

2. Learning objectives -
fertilizers
 7.6 State what is meant by the terms ‘organic fertiliser’
and ‘inorganic fertiliser’ and list TWO examples of
EACH.
 7.7 State TWO benefits and TWO limitations of using
organic fertilisers and inorganic fertilisers.
 7.8 State what is meant by: single or straight fertilisers;
compound fertilisers. List TWO examples of EACH
 7.9 State what is meant by the terms
 ‘Base dressing’, ‘Top dressing’, ‘Liquid feed’ and
‘Foliar feed’. Describe ONE situation where EACH
type of fertiliser application would be appropriate.
 7.10 Describe the use of Controlled Release Fertiliser
(CRF) granules and state TWO benefits and TWO
limitations of their use in growing media.

3. Learning objectives –
alternative growing media
 8. Understand the uses of alternative growing
media
 8.1 Describe the range of compost types available, and
the use of EACH of these growing media as
alternatives to growing in soil: including peat-based,
loam-based, peat-free, multipurpose, ericaceous, seed
and cutting and container composts.
 8.2 State how air-fill porosity, water holding capacity,
and stability of growing media affect plant growth
 8.3 Describe the environmental implications of the use
of peat, coir and municipal green waste in growing
media.

4. Fertilizers – soil testing
Three approaches
• Rule of thumb – suitable for non-
cropping situations.
• Follow fertilizer intervals recommended –
e.g. N each year perhaps several times,
P annually and K every second or third
year.
• Soil testing – macro only (DIY) or full
nutrient analysis via laboratory.
Required to diagnose excess/deficiency
accurately.

5. Fertilizers – organic and
inorganic
 Organic fertilizers are made from once living
materials (Fish, Blood and Bone etc).
 Inorganic fertilizers are derived from non-
living sources such as rocks (Phosphate) or
by synthesis from fossil fuels (e.g. Nitrogen
via the Haber process).
 Do not confuse with ‘organic’ growing
practices
 Fertilizers may be ‘straight’ (single nutrient)
or ‘compound’ (more than one nutrient).

6. Organic fertilizers – sources and
characteristics
Fertilizer Characteristics
Bone meal – heat
treated crushed animal
bone. A compound
fertilizer
Some Nitrogen, mostly
phosphorous, no
potassium. 4:15:0 (4%
N: 15%P;0% K)
Fish, blood and bone
(compound)
Contains all three
macro-nutrients (with
the potassium coming
from rock potash) 5:5:6
Wood ash Potassium – the only
organic source of
potassium at about
6% by dry weight

7. Organic fertilizers – advantages
and disadvantages
Advantages Disadvantages
Slow release – so less
risk of leaching
Requires microbial
activity
Recycles food
production waste
Low concentrations of
nutrients per volume
Encourages beneficial
soil organisms
May attract vermin.
Lower soil salinity
after use
Powder (meal) less
easy to spread evenly

8. Inorganic fertilizers – sources
and characteristics
Sodium Nitrate
(Straight)
About 16% N by dry
weight (as nitrate)
Triple Super
Phosphate (Straight)
43% Phosphorous
Potassium Chloride
(Straight)
60% Potassium
Growmore
(compound)
7: 7: 7 (7% N: 7% P
and 7% K)

9. Inorganic fertilizers –
advantages and disadvantages
Easy to get exactly
what is required
High consumption of
fossil fuels – releasing
CO2.
Water soluble –so soil
temperature not
crucial
Will leach readily if
applied at the wrong
time or in excess.
Very concentrated so
less needed
Increases soil salinity
with regular use.
Cheap ‘Straights’ are easy to
over apply

10. Application methods
 Base Dressing – applied before planting
 Top Dressing – applied to existing planting.
 Foliar Feed – solution sprayed onto and
taken up by the leaves.
 Liquid feed – solution applied diluted to the
growing media or soil.
 Controlled Release Granules or tablets –
compound fertilizer in polymer shell.
Release over time triggered by soil
temperature.

11. CRF – advantages and
limitations
Release linked to soil
temperature and
growth rates.
Expensive
Reduced leaching Polymer remains in
soil and decomposes
slowly
Single application –
less work
Single application –
hard to adjust later
Avoids high salinity in
containers – unlike
liquid feed
Not ideal for open
ground – due to
above.

12. Alternative Growing Media –
basic concepts
 Air Filled Porosity – the percentage of
pores in the growing media that will hold
air once gravitational water has drained.
 Water Holding Capacity – used to describe
the water content after drainage.
 Bulk Density – weight per unit volume
 Stability – ability of the media to form and
retain a good structure over time.

13. Nutrient Content and pH
 The nutrient content of growing media
varies according to their use. For
example cuttings compost contains no
added nutrients and seed compost very
little (perhaps a little added phosphate).
Multi-purpose compost contains N, P
and K.
 pH varies though most are
approximately neutral. Calcifuges will
need ericaceous compost which is
acidic.

14. Materials used – Peat based
 Has good AFP and low Bulk Density,
making it cheap to transport. Good WHC
but hard to re-wet once dried out. Usually
contains re-wetting agent because of this.
 Peat contains no nutrients of its own so it is
easy to add what is required.
 Environmentally problematic due to
destruction of wetlands and CO2 emissions
from processed peat and drained bogs.

15. Materials – peat alternatives
 Coir – made from coconut husks; good AFP
and WHC. Re-wets easily, unlike peat. Low
Bulk Density. Has been criticised for relatively
rapid decomposition though this may be down
to quality. Low in nutrients in original state
 Wood waste – composted bark or sawdust.
Good AFP and WHC. Higher Bulk Density than
peat or coir. Low in nutrients.
 Composted Green Waste – variable AFP and
WHC (though British Standard now introduced).
High in nutrients so not suitable for seed or
cuttings mixes.

16. Loam based growing media
 John Innes is the name of a standard formulation – not
a brand name.
 There are JI seed, cuttings, potting and general use
composts.
 Based on sieved loam, peat and sand with added lime
and variable amounts of JI Base Fertilizer depending on
use.
 High Bulk Density makes them suitable for long term
planting (but harder to handle and more expensive to
transport); medium AFP and good WHC (dry out less
easily than organic media).
 Ericaceous version available.

17. Learning Outcomes -
Fertilizers
 7.6 State what is meant by the terms ‘organic fertiliser’
and ‘inorganic fertiliser’ and list TWO examples of
EACH.
 7.7 State TWO benefits and TWO limitations of using
organic fertilisers and inorganic fertilisers.
 7.8 State what is meant by: single or straight fertilisers;
compound fertilisers. List TWO examples of EACH
 7.9 State what is meant by the terms
 ‘Base dressing’, ‘Top dressing’, ‘Liquid feed’ and
‘Foliar feed’. Describe ONE situation where EACH
type of fertiliser application would be appropriate.
 7.10 Describe the use of Controlled Release Fertiliser
(CRF) granules and state TWO benefits and TWO
limitations of their use in growing media.

18. Learning Outcomes –
Alternative Growing Media
 8. Understand the uses of alternative growing
media
 8.1 Describe the range of compost types available, and
the use of EACH of these growing media as
alternatives to growing in soil: including peat-based,
loam-based, peat-free, multipurpose, ericaceous, seed
and cutting and container composts.
 8.2 State how air-fill porosity, water holding capacity,
and stability of growing media affect plant growth
 8.3 Describe the environmental implications of the use
of peat, coir and municipal green waste in growing
media.