Agriculture Reference
In-Depth Information
Table 15.1
Alternatives to peat
with descriptions of those on the market, their
performance across a range of plants and cost.
X
Seed and cutting composts
are more precisely
adjusted for use with seeds, particularly fi ne seed,
and cuttings that benefi t from having fi ner, more
closely graded components and lower soluble
nutrient content, although phosphate levels are
maintained (see p. 166). Lime is added, so these
composts are not suitable for calcifuges ('lime-
hating', ericaceous plants).
X
Container composts
tend to be coarser, less
closely graded and while usually suitable as a
potting compost, it is appropriate for the larger
plants being grown in larger containers. Lime is
added so again these composts are not suitable for
calcifuges ('lime-hating', ericaceous plants).
X
Ericaceous mixes
are specifi cally designed for
calcifuges ('lime-hating', ericaceous plants).
Organic materials
Inorganic materials
Coir
Garden compost
Perlite
Green waste
Polystyrene
Leaf mould
Rockwool
Recycled landfill
Sand/grit
Straw
Vermiculite
Vermicomposts
Wood chips/fibre
Woodwastes
they are formed but any one type is usually very
uniform, such as
sphagnum moss peat
. This is less
decomposed than other types of peat and has the
ideal open structure for plants in containers.
Great efforts are being made to find
alternatives to
peat
in order to preserve the wetland habitats where
peat is harvested in Britain and Ireland and beyond.
This peatland is also a significant carbon store that
releases greenhouse gases (carbon dioxide) once
it is made suitable for plants. The use of peat is not
sustainable because it develops so slowly (see p. 7).
A list of some of these alternative materials is given in
Table 15.1.
A very wide range of loamless composts is available
for both the amateur and the professional grower,
but they broadly fit in to the following main
categories:
X
Multipurpose composts
, as their name suggests,
have been formulated for a wide range of
purposes. The components are suffi ciently fi ne to
ensure successful growing from seed or cuttings
while having suffi cient air-i lled porosity to grow
larger plants on in a range of containers. These
'all-purpose' composts have a balance of nutrients
that meets the needs of most plants grown in
containers. There are suffi cient nutrients to get
the plants started, but additional feeding is usually
needed after about a month. There is usually
advice available as to what and how to add more
nutrients ('feed') as the season progresses. Lime
has been added to these, so these composts are
not suitable for calcifuges ('lime-hating', ericaceous
plants).
Most are now 'peat free' or 'reduced peat' which
means that they are made up of a variety of
ingredients. There are many on the market and
they vary in performance and cost. Research
continues and improvements are being made all
the time. They are reviewed quite frequently in
the consumer magazines and the gardening press
Plant containers
There is an enormous range of containers used to
meet the many different requirements of growing
plants (see Figure 11.3).
Plastic containers predominate, with a variety of
shapes and sizes. Most are very functional, but
there are many decorative containers available with
advantages in terms of lightness and cost. The
black ones tend to heat up more than the standard
terracotta-coloured ones and the contents of white
plastic pots can be as much as 4°C lower than in
other colours. Pots of white or light green plastic can
transmit sufficient light to affect root growth adversely
and encourage algal growth.
Clay pots are porous and water is lost from the
walls by evaporation. Consequently, clay pots dry
out more rapidly than plastic ones, especially in the
winter and, although air does not enter through the
walls, this can help to improve air-filled porosity.
The higher evaporation rate also keeps the clay
pots slightly cooler, which can be beneficial in hot
conditions.
Biodegradable containers such as those made
from paper have become popular because they
can be planted directly. Some materials decompose
more rapidly than others and there can be a
temporary lock-up of nitrogen, but most such
containers are now manufactured with added
available nitrogen. It is essential that these containers
are soaked and the surrounding soil is kept moist
after planting, or the roots will fail to escape from the
dry wall.
