Agriculture Reference
In-Depth Information
Other trace nutrients
Copper, boron, zinc, manganese and molybdenum
are essential nutrients that are required in minute
quantities and are rarely deficient in cultivated soils in
Britain and Ireland. They are added as supplements to
some growing media made up of materials with little
or no trace nutrients present.
Providing plant nutrients
In nature the recycling of nutrients ensures the
continued growth of plant communities (see p. 34)
unless there are net losses through leaching. This
can also be the situation in some gardens, especially
where plantings are similar to natural ones, such as
predominantly trees and shrubs. In practice, even
in decorative gardens there is a need to import
some nutrients. There are significant differences in
maintaining a lawn where mowings are allowed to
stay on the lawn (recycling) compared with one where
the arisings are 'boxed off' (i.e. collected and not put
back). Most gardeners make good the nutrient losses
with their garden compost (see p. 164), brought in as
composted municipal waste, manures (see p. 172)
and/or fertilizers.
Organic gardeners and growers put the emphasis on
the recycling of organic matter including composting
(see p. 160) and minimizing the use of artificial
(synthetic) fertilizers. They can only make good
nutrient loss by crop removal through the importation
of manures (under strict rules about the sources
if organic status is to be maintained) or the use, in
strictly prescribed circumstances, of a limited range of
('permitted') fertilizers.
14
Figure 14.6 Lime-induced iron defi ciency on
Elaeagnus x ebbingei . Note that it is the younger
leaves that have chlorosis (yellowing) while the older
leaves are still green
Iron (Fe)
Iron is involved with chlorophyll production. Although
it does not form part of the chlorophyll molecule, it is a
component of some enzymes required to synthesize it.
Deficiency of iron results in yellow ('chlorosis') or
even white leaves appearing in the younger leaves
first. The deficiency is commonly caused by the
presence of large quantities of lime (see p. 176).
This ' lime-induced ' chlorosis (Figure 14.6) occurs
on over-limed soils and chalky soils; calcicoles are
adapted for the chalk and limestone areas, but other
plants grown in such conditions do not fare well and
have a typically yellow appearance. Good drainage
and soil structure should be maintained as a water-
logged root zone can contribute to the problem of an
iron deficiency.
Iron fertilizer or supplement in the form of ferrous
sulphate is commonly added in small quantities to
amenity turf to 'green up' its appearance without
the need to add more nitrogen. Chelated iron is a
supplement that can be used as a precaution or to
treat affected plants being grown on an unsuitable
growing medium.
Fertilizers are concentrated sources of plant
nutrients that are added to growing media.
Manure is a source bulky organic matter
comprising animal faeces and bedding.
Organic sources of nutrients
Organic in its original sense meant chemicals
derived from organisms, that is, living things. The
idea that there are chemicals that could only be
made this way was shown to be false when urea
was synthesized from inorganic ingredients in 1828.
'Organic chemistry' is now more commonly referred
to as 'Carbon Chemistry', that is, the chemistry of all
compounds containing carbon atoms. See companion
website: www.routledge.com/cw/adams.
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