Transcript Slide 1

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As rocks break down mineral ions are
released in soluble form
Held on surface of small particles
Can be accessed by root hairs
They are held in organic matter
In living or dead organisms
 Waste products
 Finally as humus
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Released as ions (anions and cations)
Available for other organisms
Plant nutrients
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Rocks break down as result of:
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Wind, water
Seismic movement
Molecules removed from outer surface of
particles
Are held in solution around the particle
 Will wash away (by leaching) or
 Can be taken up by plants (and other organisms)
 Returned to soil afterwards by decomposition
 Forms what we call soil!
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Retained by: 
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Becoming attached to soil particles or in solution
Being held in humus
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Clay and humus have negatively charged sites
Sites hold positively charged ions on their
surfaces
This protects the ions from leaching and loss
CEC is the measure of the ability to retain soluble
ions in the plant root zone.
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These ions are rapidly exchangeable with other soluble
ions
When root uptake depletes the nutrient supply they
replenish plant-available cations in the soil solution.
Cation exchange is a major source of nutrients e.g.
Major nutrient K+, Ca2+, and Mg2+,
 Ammonium NH4+
 Micronutrient trace metals like Zn2+, Mn2+, and Cu2+
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The ‘soil cations’ essential for plant growth
include ammonium, calcium, magnesium, and
potassium.
The major distinguishing characteristic of
cations is their positive charge. Just like a
magnet, a positive charge is strongly attracted
to a negative charge. When soil particles have a
negative charge, the particles attract and retain
cations. These soils are said the have a cation
exchange capacity.
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However, most of the available nutrition is
held on the surfaces of fine clay and humus
particles. These surfaces, called exchange sites,
have a negative charge that attract and bind
positively charged minerals, called cations
In order to release a cation held on an exchange
site, some other material must first dislodge or
replace it. This is known as Cation Exchange
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150 years research has shown that crops
routinely respond well to one set of elements –
these are the macronutrients.
A 2nd set of elements don’t usually matter, but
can cause specific deficiencies. These are the
micronutrients.
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http://apps.rhs.org.uk/advicesearch/profile.a
spx?PID=456
Three main elements are need for plant growth:
nitrogen (N) to encourage good growth,
phosphorus (P) for root growth
and potassium (K) for fruit and flowers.
N, P, K [big 3]
Also Mg, S
The micronutrients
Ca, Fe, Mn, Mo, Na, Co, Si
Crucially important point: It is not enough that a soil contains
an element. What matters is its availability to plants.
Thus acid digests of heathland soils show ample levels of
nitrogen, but almost all of this is locked up in biomass or
humic materials, and in fact such soils are acutely deficient
in nitrogen.
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This is the most important plant nutrient, at least in
terms of producing a reliable and large increase in
growth.
Most of the advances in agricultural production since
the 1940s have been won by vast increases in nitrogen
application.
More N => more growth, typically soft fast sappy
growth, deep green foliage..
Deficiency of N => stunting, yellowness and general
poor growth.
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This is 2nd in effect after nitrogen.
Is always applied as phosphate
P deficiency leads to dark, stunted growth often purple tints on the leaves, also causing
poor root growth, so limited uptake of other
nutrients as well.
P promotes cell division, mechanical strength,
maturation/seed set, disease resistance.
Legumes need littleN (are fixers) but do need P
- has been suggested that a major conservation
issue in UK is phosphate eutrophication, which
leads to N enrichment.
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Is that it is immensely immobile in soil. This is
because many of its salts are highly insoluble, ie
bones! Iron, aluminium phosphates are if anything
even less soluble.
Fe3+ + PO43- => FePO4, insoluble
P fertilisers once applied can be locked up in the soil
without plants getting any benefit. Acid solutions
(such as superphosphate) are the problem: acidity
mobilises Fe, Al which them immobilise P. This
process is confusingly called phosphorus fixation.
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This is achieved by controlling soil pH,
which should be held around pH 6.5.
A prime function of liming acid soils is to
elevate the pH to the 6-7 range.
Similarly, chalky soils may need to be
acidified somewhat to increase P
availability, though this is less usual.
Soils rich in Fe(OH)3 such as tropical clays
will immobilise P whatever the pH
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trials consistently show K to be a major
determinant of plant growth.
It determines turgor, frost hardiness and
resistance to wind.
K deficient plants are stunted and yellow often the older needles / leaves are yellowest
as this mobile element is translocated to the
newest tissue.
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Are related to its mobility.
Left alone, K will rapidly leach out of soils or
litter. It is low on acid sandy or organic soils,
highest in clays.
Organisms take K up avidly, so that its
distribution is ecosystems may be defined by
biological not chemical processes.
K experiences luxury consumption - this means
that plants take up more K than they need if it
applied. It does them no harm, but does cost the
farmer money. Best fertilise little but often.
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Causes yellowing, especially of older needles /
leaves.
Is often caused by waterlogging - a
physiological problem not a chemical one.
Is cured by adding dolomite (MgCO3+CaCO3)
or purer magnesium salts.
Carbon (C)
Major constituent of all organic molecules,
Accounts for around 40% of plant dry matter.
Nitrogen (N)
Key to protein formation, amino-acids and
Enzyme systems.
Phosphorus (P) Essential to all living cells for
Sugar formation
Storage & transfer of energy.
Potassium (K)
Regulates water movement, plant structure and the transfer of
carbohydrates.
Sulphur (S)
Links with Nitrogen to form protein and is a major part of aminoacids and enzymes.
Calcium (Ca)
An essential part of cell walls and membranes, protein synthesis
and plant defence.
Magnesium (Mg)
Essential to photosynthesis, chlorophyll, cell repair and
metabolism.
Boron (Bo)
Links to Calcium and Nitrogen uptake, protein synthesis and the
formation of hormones, sugars and CHO.
Copper (Cu)
Involved in protein synthesis, seed formation, plant defence (lignin
& phenols) & chloroplast.
Iron (Fe)
Essential to enzymes involved in respiration, photo-synthesis and disease
resistance mechanisms.
Manganese (Mn)
Vital to photosynthesis, enzymes, cell repair and disease resistance
mechanisms.
Molybdenunm (Mo)
Vital to enzymes needed to regulate and control Nitrogen metabolism. (Nfixing bacteria).
Zinc (Zn)
Required for starch formation, enzyme systems, phenols and disease
resistance mechanisms.
Silica (Si)
Considered non-essential, but is involved in cell membrane formation and
disease resistance.
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Nitrogen is the most abundant element in our
planet’s atmosphere. Approximately 78% of the
atmosphere is comprised of this important
element.
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Nitrogen is required by all living organisms for the
synthesis of proteins, nucleic acids and other nitrogen
containing compounds. The Earth’s atmosphere
contains almost 80 % nitrogen gas. It cannot be used in
this form by most living organisms until it has been
fixed, that is reduced (combined with hydrogen), to
ammonia.
The nitrogen cycle is a series of processes that convert
nitrogen gas to organic substances and back to nitrogen
in nature. It is a continuous cycle that is maintained by
the decomposers and nitrogen bacteria. The nitrogen
cycle can be broken down into four types of reaction
and micro-organisms play roles in all of these.
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http://www.youtube.com/watch?feature=fvw
p&NR=1&v=R8-E6cDCr5U
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http://www.teachersdomain.org/resource/ls
ps07.sci.life.eco.nitrogen/
http://www.microbiologyonline.org.uk/about
-microbiology/microbes-and-theoutdoors/nitrogen-cycle
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Fertilisers are concentrated sources of plant
nutrients, usually in compact form such as
pellets, granules, powders or liquids. They are
used to improve plant growth and yields.
Most fertilisers are based on the three major
plant nutrients:
Nitrogen (N): For green leafy growth
Phosphorus (P): For healthy root and shoot
growth
Potassium (K): For flowering, fruiting and
general hardiness
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There are many different types of fertiliser available, including
liquid tonics that can be applied from a watering can, granular
fertilisers that are mixed into compost and powdered feed that is
applied to the soil. These feeds work in three main ways:
Controlled release fertiliser – ideal for containers, these come as
granules that are mixed into compost and release their nutrients
over a long period of time, some for up to 12 months. Plugs made
from granules bonded together are also available - these can
simply be pushed into the surface of the compost.
Slow release fertiliser – good for feeding plants in the soil. Usually
applied as a powder that can be scattered around perennials,
trees, shrubs and vegetables.
Fast acting fertiliser – for plants in need of a pick-me-up. These are
ideal if a plant is suffering from a deficiency and are usually
applied in a liquid form that can be used by the plant quickly.
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Top dressing
Base dressing
Watering on:
Foliar feeding:
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http://www.bfs.uk.com/content/BFSNDIGui
de.pdf
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Exercise 2
Work in groups of two
List what we can do to alter the
nutrient availability in the soil
To increase:To decrease:-
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http://soils.usda.gov/sqi/publications/files/
biodivers.pdf
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If you suspect that a plant may be suffering from a nutrient
deficiency, but are not certain which nutrient it is, use the
symptoms below as a quick reference. To confirm the diagnosis,
look up the more detailed descriptions of the symptoms and
problem soils etc. under the separate heading for the individual
nutrients.
Leaves pale green, plants stunted - Nitrogen
Leaves with purple or bronze tints - Phosphorus
Marginal discolouration/scorch - Potassium
Leaves yellow, veins green Iron, magnesium (also see manganese)
Dark water-soaked areas on fruit, brown pitting, internal
browning, brittle tissue - Calcium or boron
Narrowing of leaves (brassicas) - Molybdenum
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Types of fertiliser
Fertilisers are available as solid, liquid or
soluble formulations. They may either be quick
acting or have a slow or controlled release
mode of action. The differences of each type
and when to use them are explained below.
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Inorganic or Chemical fertilisers are available in powder or
granular form. They release nutrients readily - but are not quick
acting.
Organic fertilisers such as blood and bone meal and fish and bone
meal are slower acting since they need to be broken down by soil
bacteria before the nutrients are available to the plant. Solid
fertilisers are generally used as pre-sowing or planting fertilisers
or routine top dressings. They are less useful where plants are
suffering from a nutrient deficiency because of the time it takes for
plants to be able to absorb and then use the nutrients.
Solid fertilisers require good soil moisture to transport the
nutrients to plant roots. Thus, in dry periods, watering will be
necessary. The main benefits of solid fertilisers are their
familiarity, ease of application and the fact that they are usually
cheaper per unit of nutrient.
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Are quicker acting, especially if they can be
applied as a foliar feed. This is an important
consideration when treating nutrient
deficiencies. They are a better option in dry
weather although in wet weather, the nutrients
can be more easily leached through the soil.
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Contain one key nutrient , are suitable if the
crop needs a particular plant nutrient in
preference to others, either because of a
deficiency problem or if a crop has a
particularly high demand for an individual
nutrient. These fertilisers are relatively
inexpensive and are often used by 'traditional'
growers.
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are available in different formulations to suit
different types of users. Some are available as
concentrated liquids or soluble powders for
dilution by the user. These tend to be more cost
effective.
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are extensively used by plant growers - they
are easy to use and effective, provide plants
with nutrients for a whole season and release
nutrients at times when plants have the
greatest demand for them. They are
particularly useful for containers and hanging
baskets. They are put into the containers at
planting time and perform well throughout the
season, without the need for supplementary
feeding.
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Nitrogen (N)
Nitrogen is an essential nutrient in most plant
functions; it is the key constituent in proteins
and in chlorophyll and thus is especially
important for healthy growth of leaves and
other green parts of plants. Good leaf growth is
essential for good yields. Deficiency
symptoms: Stunted growth, pale green/yellow
leaves and general lack of vigour. Symptoms
appear on older leaves first.
Phosphorus (P)
Phosphorus, normally expressed as phosphorus
pentoxide (P205) on the label, is important for many
plant functions, particularly healthy root growth. It
also plays a significant role in encouraging good
germination of seeds, seedling development and fruit
ripening. Deficiency symptoms: Leaves develop
blue/green or purplish tints; dead leaf tissue can occur
when deficiency is severe. Leaves are reduced in size.
Older leaves are the first to be affected and may drop
prematurely.
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Potassium or Potash (K)
Potassium, expressed as potassium oxide (K20)
on the label, plays a major role in ensuring high
quality and abundant fruit and flowers.
Deficiency symptoms: Older leaves are the
first to be affected. Symptoms are brown or
purple leaf edges and the leaf margins may
curl up or downwards.
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A question of balance
When plants suffer from lack of nutrients, they
show symptoms of being unhealthy.
To allow plant roots to obtain these
nutrients from the soil firstly it must be
sufficiently moist to allow root uptake.
Second, the pH of the soil must be within a
certain range for nutrients to be released (see
chart on page 6).
Third, the soil temperature must be within
a certain range for nutrient uptake to occur.
The optimum balance of temperature, pH and
moisture will differ from one species of plants
to another so nutrients may be physically
present in the soil, but will not be available to
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plants.
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http://www.bfs.uk.com/content/BFSNDIGui
de.pdf
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Macronutrients
nitrogen
 potassium
 magnesium
 calcium
 phosphorus
 sulphur
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Micronutrients
or
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Trace elements
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Iron
Zinc
Molybdenum
Manganese
Boron
Copper
Cobalt
Chlorine