KNOW-HOW
GARDENING AUSTRALIA SEPTEMBER 2019 55
A number of Australian native plants
have evolved in low-phosphorus soils,
so most native fertilisers stay on the safe
side and contain little or no phosphorus.
Camellia and azalea foods are
formulated to suit the acidic conditions
favoured by these plants.
Fertilisers are either derived from natural
sources or synthetically manufactured,
and some are a combination of both. If you
want to grow an organic garden, look for
organic certification on the pack. Although
these products are more expensive, you
can be sure that organic certification is
strictly controlled in Australia.
Here are the different types of fertilisers
available and how they work:
Compost and manures make wonderful
soil conditioners, as they encourage
microbial activity, improve soil structure and
increase the soil’s moisture- and nutrient-
holding capacity, but they are relatively low
in nutrients. Some manufacturers process
manure into pellets, thereby slowing the
nutrient release, and chemical nutrients
are sometimes added at this stage.
Blood and bone releases very slowly and
generally doesn’t contain a measurable
amount of potassium, so extra potassium
is often added to this natural fertiliser.
Inorganic fertilisers are sometimes
termed chemical or synthetic fertilisers,
and come in granular or slow-release
forms. They tend to be good sources of
nutrients but are based on fertiliser salts,
so can damage soil and plants if not applied
with care and according to the label.
CLOCKWISE FROM OPPOSITE
Yellowing leaves often mean it’s time for
a handful of controlled-release fertiliser;
soluble fertilisers dissolve easily in water and
offer a quick nutrient boost to most plants;
applied before planting, blood and bone
provides a gentle, slow release of nutrients.