Should you use
organic or inorganic fertilisers?
Sometimes advice from
garden experts seems to be at best confusing and at worst contradictory.
For example, many garden advisers only advocate 'organic' fertilisers,
while others don't use this term. What do they mean, and what is
an organic fertiliser?
Well, definitions can
be as vague as some of the advice but, generally, an organic fertiliser
is said to be one that is derived from living material or from a
natural source. This includes animal manure and blood and bone.
From the plant's point
of view it doesn't really matter whether its source of nitrogen
and other nutrients is organic or manufactured, but if the idea
of using an organic plant food is appealing, the easiest way
to do so is by buying and applying some blood and bone or sheep
Yates Nature's Way Organic
Sheep Pellets, for example, are made from pelletised sheep manure
and wool waste. As well as being a gentle source of nutrients, the
pellets make an excellent soil conditioner. They improve moisture
retention and, like most other organic matter, they help to aerate
The nutrient release
from pellets is relatively slow because sustained microbial activity
is required to break down the organic matter. This slow release
means that the pellets continue feeding plants over a long period
and there is almost no risk of the plants suffering from fertiliser
The other really popular
organic fertiliser is blood and bone. Blood and bone is made from
waste material and is a gentle source of nitrogen, phosphorus and
calcium. It doesn't, however, contain any potassium (which is one
of the most important plant nutrients) so, if you're using it to
feed vegetables, it's a good idea to add some extra sulphate of
potash (approximately one part of sulphate of potash to ten parts
of blood and bone).
Plants, just like us,
get bored if they're given the same food all the time, so, for optimum
plant health, it's best to vary their diets by including some inorganic
A fertiliser such as
Thrive Soluble All Purpose is dissolved and applied in liquid form
and, as a result, it promotes a very rapid growth response. Thus,
it's a particularly appropriate choice for fast-growing plants such
as flower and vegetable seedlings.
Granular plant foods
are concentrated dry fertilisers that have been specially formulated
for different plant groups such as roses, citrus and camellias and
azaleas. Granules should always be applied to moist soil and
watered in well immediately afterwards. They can supply plants with
a customised diet.
There's no real answer
to what's the best type of fertiliser. For plants, just as for people,
variety is the spice of life. The real clue is to select a trusted
brand of fertiliser so you can be sure you're getting the very best
quality for your plants.
with permission from NZOOM Home and Garden content,
from the previous
The views expressed here are not necessarily those of the RNZIH