Leaving Certificate Ag. Science – Grassland
Grassland
~ Introduction and Varieties ~
1. Introduction
Grassland occupies 70% of the world’s
agricultural land, making it the world’s most
important crop.
In Ireland, grass provides 70 – 80% of our
cattle’s feed requirements and over 90% of our
sheep’s.
2. Categories of Grassland
There are three main categories of grassland.
a. Rough Mountain and Hill Grazing:
More appropriately called grazing than
grassland as most of the land is taken up with
heather, gorse, bracken and scrub rather than
grasses.
It is characterised by large range in
composition, low stocking rates and low
production.
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Leaving Certificate Ag. Science – Grassland
The land is usually acidic or peaty and generally
stony.
It can therefore be very difficult or impossible to
cultivate.
b. Permanent Grassland
This is grassland that is never ploughed.
It is different from Hill Grazing because it is
dominated by perennial grasses and scrub, and
trees are rare.
It again displays a large range in botanical
composition from highly productive grasses to
clover to highly unproductive weeds.
Generally permanent grassland is more
productive than mountain and hill grazing areas
and is also more highly stocked.
c. Leys
These are short term areas of grassland, sown by
the farmers which display the following
characteristics:
Little variability in botanical composition
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Leaving Certificate Ag. Science – Grassland
High stocking rates
High levels of production.
Leys are associated with good farm practices
and high levels of management and are resown
and reseeded regularly.
3. Grassland Distribution
Grass dominates most of the land in nearly all
the counties in Ireland.
In Munster, Ulster and Connaght it can be up
to 90% of all agricultural land.
In the south – east it is only about 75%. Why?
The following table shows the relative amounts
of grassland in Ireland.
Category of Grassland
Area (Ha, millions)
% of Agricultural Land
1. Mountain / Hill Grazing
1.04
18.2
2. Permanent Grassland
2.93
51.3
3. Leys
1.24
21.7
4. Grassland Ecology
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Leaving Certificate Ag. Science – Grassland
The natural vegetation in Ireland is deciduous
forest.
This basically means that if all agricultural and
industrial activity stopped, the land would
eventually return to forest.
The stages of progression are as follows:
a. Bare Soil
b. Grasses
c. Shrubs (Bramble, hawthorn and Blackthorn)
d. Forest species like Oak, Ash, Birch and other
trees which eliminate shrubs by their shading
effect.
Intensive grazing prevents this series of activities
to take place.
This is because grass species can regenerate
from points below the grazing level.
If grazing was reduced or stopped, shrubs
would take over and then eventually trees.
This is important as the farmer must manage his
/ her grassland so as to ensure that unwanted
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Leaving Certificate Ag. Science – Grassland
shrubs don’t take over the area.
5. Important Agricultural Grass Species
Between 200 and 300 species of grass exist in
Ireland but only a small number are of any real
importance to the farmer.
Some of the common species found in the
different types of grassland are shown below:
a. Hill and Mountain Grazing:
Heathers
Purple Moor grass
Bent Grasses*
Sheep’s Fescue*
Creeping Red Fescue*
Meadow Grasses*
b. Permanent Grassland:
Bent Grasses*
Fescues*
Meadow Grasses*
Cocksfoot*
Meadow Fescue*
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Leaving Certificate Ag. Science – Grassland
Timothy*
Perennial Ryegrass***
White Clover**
c. Leys:
Cocksfoot*
Timothy*
Perennial Ryegrass***
Short Duration Ryegrasses***
White Clover**
Red Clover**
The asterisks determine the palatability and productivity of
the species.
Some of the most important grass species will
be studied in more detail:
i.
Perennial Ryegrass
The most valuable and important grass in Irish
farms.
Makes up to 85% of the total grass seed sold
each year to Irish Farmers.
It has a shiny dark green colour, which gives
the sward a glistening sheen.
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Leaving Certificate Ag. Science – Grassland
ii.
Italian Ryegrass (Short – Term Ryegrass)
Similar in appearance to perennial ryegrass but
has awned seeds
A more erect growth habit and less aggressive
growth pattern.
It is however the highest producing grass,
nearly 20% more than perennial.
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Leaving Certificate Ag. Science – Grassland
iii.
Clovers (White and Red)
Clovers are legumes which mean that they
can fix Nitrogen.
This generally means that they can change
atmospheric Nitrogen into forms that the soils
can absorb and use.
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Leaving Certificate Ag. Science – Grassland
Therefore they are of huge importance to the
farmer and they improve the quality of the
sward and soil.
However they can have a negative reaction to
artificial fertilisers that contain Nitrogen.
They also have deep roots and spread
throughout the soil by stolons, which then
inhibit weed growth.
iv.
Other Important grasses
While perennial ryegrass, Italian ryegrass and
clovers supersede all other grass species in
seed sales each year, there are other
important species.
These include: Timothy, Cocksfoot, Meadow
Fescue and Meadow Grasses.
These were traditionally used many years ago
but are still very important in permanent
grasslands.
Farmers should be able to recognise them and
encourage their growth.
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Leaving Certificate Ag. Science – Grassland
Use your book for more detail on these
varieties.
Below are the inflorescence of a) Timothy, b)
Meadow Fescue, c) Cocksfoot and d)
Meadow Grass
6. Determining Agricultural Importance of Species
Grassland in Ireland is used solely for feeding
livestock.
Therefore the agricultural importance of any
grassland is measured in three ways:
Productivity, Palatability and Digestibility.
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Leaving Certificate Ag. Science – Grassland
Productivity refers to the ability of a grass to
produce large amount of herbage.
It also refers to the ability to respond to a
fertiliser.
Perennial ryegrass has the highest productivity
while mat grasses have low productivity.
Palatability refers to taste etc, in other words
how appealing the grass is!
Sheep and cattle are selective eaters and will
only eat the most palatable grass.
Therefore the sward should be made up of
appealing varieties.
PRG and IRG are the most palatable grasses
followed by cocksfoot.
Digestibility is a rating of the ability of an
animal to digest a certain feed.
It is measured in terms of DMD (Dry Matter
Digestibility) – how much of the dry matter the
animal can digest.
Digestibility of grass varies throughout the
grass’s year also.
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Leaving Certificate Ag. Science – Grassland
Before flowering the DMD may be 80 – 90%,
and after flowering as little as 50%.
7. Seed Mixtures
Seed mixtures are very different for grassland
as opposed to silage.
In previous years it was usual practice to sow a
number of different varieties as to have a
uniform grass growth throughout the year.
This has changed over the last number of
years, towards mainly ryegrasses and clovers.
This is mainly due to the emergence of new
strains of perennial ryegrass, which have
different peak growth times.
Now seed mixtures for grazing have different
strains of PRG, which have a range of heading
dates.
This gives the following advantages:
1. Encourages uniform growth patterns
2. Ensures there is always young, leafy
digestible grass available as feed.
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Leaving Certificate Ag. Science – Grassland
3. Makes grazing management easier – all the
grass can’t go “stemmy” at the same time.
For silage or hay, seed mixtures contain either
strains with the same heading dates or seeds
from the same strain only.
This is to ensure that the entire sward comes to
a head at the same time.
This gives a sward that is all at the height of its
digestibility when cut.
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Leaving Certificate Ag. Science – Grassland
Grassland
~ Grazing Management ~
1. Methods of Sowing
There are four main methods of sowing leys:
i. Direct Sowing
Best and most reliable way to obtain a
ley.
The seedbed is prepared by ploughing
and harrowing.
It should be very fine, finer than that for
cereals.
Fertiliser should be broadcast and
worked in during the final seedbed
preparation.
The seed is sown using a combine drill, in
lines 10cm apart and 2cm deep.
They may also be broadcast over the soil
and covered over using a chain harrow.
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Leaving Certificate Ag. Science – Grassland
The land should be rolled after sowing to
improve seed – soil contact and better
germination rates.
Spring sown leys should be sown before
May 1st due to the risk of drought.
Autumn sown leys should not be sown
after Mid – September.
ii. Undersowing
Undersowing is used by farmers who
employ tillage / grass rotations.
The grass seeds are grown with the
tillage crop, usually a spring cereal.
Over the summer the two crops grow
together and after harvesting, the grass
takes over.
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Leaving Certificate Ag. Science – Grassland
The land should be autumn ploughed
and the seedbed prepared in the usual
manner.
The grass is sown directly after the cereal
(using a drill) and then the land is rolled.
Spring Barley is the most suitable “nurse
crop” as the competition between the
two crops is less due to short straw and
early harvesting.
Lodging is a problem with this method,
so N application should be lessened by
30%.
Tillage yields are reduced using this
method also.
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Leaving Certificate Ag. Science – Grassland
Undersowing grass with arable silage
(oats / vetch) is good farming practice.
The silage is cut early and the grass has a
good chance of establishing itself.
iii. Direct Drilling
This technique involves drilling seeds into
unploughed ground.
The drilling machine cultivates a small
strip of soil and sows the seed in it.
No problems occur if direct drilled into
stubble.
But if direct drilling into grassland,
problems and/or competition can occur.
The grassland should be grazed bare or
mown and killed with a herbicide before
direct drilling.
Slug pellets and fertiliser are added with
the seed in order to help its
establishment.
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Leaving Certificate Ag. Science – Grassland
Direct drilling is most successful on
shallow soils where ploughing is difficult.
iv. “Stitching In”
This system is almost the same as direct
drilling, except the old sward is not killed.
The seed is drilled using a similar drill,
along with slug pellets and fertiliser.
If the seeds establish themselves then
they become the dominant species in
the sward.
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Leaving Certificate Ag. Science – Grassland
This system is not as predicable as direct
drilling and the old sward can often win
out.
2. Grassland Establishment
This refers to the development of the seedlings
into a thick, densely packed pasture.
The most significant process in the
establishment of a good sward is tillering.
Tillering is promoted by damage to the main
shoots of the plants.
Newly sown pastures should be lightly grazed
to encourage tillering and promote growth.
The best animals for this are sheep or calves, as
cows would damage the crop.
This works well for spring sown grassland (not
undersown), as the land is dry when grazed.
Annual weeds can be controlled by grazing or
topping, as tillering is then promoted and the
weeds get little chance to establish
themselves.
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Leaving Certificate Ag. Science – Grassland
Perennial weeds like dock can be partially
controlled by topping, but a selective
herbicide may be required in extreme cases.
3. Grassland Management
Good Grassland Management involves the
following:
1. Finding out the amount of herbage
required.
2. The application of ample fertiliser to
achieve this.
3. Maximising the DMD of the sward by
managing grazing and
conservation.
The amount of herbage output required is
calculated by the amount / type of stock on
the farm.
Generally 1 livestock unit consumes 12 tonnes
of herbage dry matter per year.
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Leaving Certificate Ag. Science – Grassland
A. Fertiliser Requirements
The amount of fertiliser applied to grassland
greatly depends on the grazing level and the
level of establishment.
Fertiliser should be applied to newly
established grassland where grazing is light, in
the following proportions:
N – 48 kg / ha
P – 20 kg / ha
K – 38 kg / ha
Intensely grazed pastures should receive
additional fertiliser as outlined by Teagasc.
Land set aside for silage or hay should also be
fertilised in advance of each harvest.
Hay is only cut once over the grazing season
while silage can be cut repeatedly.
The following is recommended by Teagasc:
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Leaving Certificate Ag. Science – Grassland
B. Managing Grazing
Good grazing management requires young
leafy digestible grass to be available for
grazing at all times.
An efficient system of rotational grazing allows
the farmers achieve this.
There are various systems available and below
are details on some of the common systems
used in Ireland:
i. Paddock Grazing
Paddock grazing is the most efficient form of
rotational grazing, whereby 20 – 25
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Leaving Certificate Ag. Science – Grassland
paddocks are created using electric
fencing.
The paddocks are created to suit the herd,
using the rule: 120 cows will graze 1 ha of
young leafy grass in one day.
The herd graze one paddock per day in a
rotational manner.
Nitrogen is applied to the paddocks as soon
as they are removed.
By the time they return to the paddock, the
grass should be at the height of its
digestibility.
This system can be quite expensive but is
widely used on dairy farms.
Silage fields are usually kept independent of
the paddock system, as the small areas may
be difficult to cut.
Calves & replacement heifers graze any
replacement grass.
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Leaving Certificate Ag. Science – Grassland
ii. Strip Grazing
This system involves the use of a movable
electric fence, to give the stock a fresh strip
of leafy grass per day.
Grass strips are fertilised in the same way as
the paddock system.
A back fence should be used however, as to
allow the grass recover sufficiently.
This system is cheap, but requires a lot of
labour time and is therefore rarely used by
itself.
iii. Set Stocking
This is simplest, cheapest but least effective
form of grazing management.
It simply involves allowing the stock free
access to all areas throughout the grazing
year.
This allows set – stocked areas to become
patchy, with areas of highly un-productive
grasses evident.
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Leaving Certificate Ag. Science – Grassland
iv. Block Grazing
This system is the most common system used in
Ireland, as it is cheap, effective and low on
labour.
It involves the division of the grazing area into
blocks that provide grazing for 7-8 days.
Pasture management can be improved by
using strip grazing in each block.
Larger blocks can be set aside for silage once
or twice a year.
This system is cheap and is suitable for dairy,
beef and sheep grazing.
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Leaving Certificate Ag. Science – Grassland
Grassland
~ Conservation ~
1. Introduction
Grass conservation involves the restricting of
bacterial growth and other organisms, which
would otherwise cause spoilage.
This can be achieved by two contrasting
methods:
i. Controlled Fermentation – reducing
the pH (acidity) of the grass to a level
where growth of bacteria is inhibited.
ii. Dehydration – removing the level of
water to inhibit microbial activity.
Silage is produced by the means (i)
above while hay involves dehydration.
Silage is much more independent of the
weather, so this makes it a better system for
Irish farmers.
Grass can be cut for silage in May, when the
grass is at its most digestible (highest DMD).
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Leaving Certificate Ag. Science – Grassland
Hay cannot, however, as long periods of good
weather cannot be expected.
Hay is allowed to grow to a more mature
stage and is generally cut in June where the
weather is warmer.
Therefore hay has less food value than silage.
Silage making is more expensive though but
the product is of a higher quality.
Silage accounts for nearly 70% of conserved
grassland now (45% in the 1970’s).
2. Silage Production
a. Biochemical Processes
When grass is cut and placed in a heap,
respiration continues to occur.
Respiration is the burning of Carbohydrates
to CO2 and Water.
This means that food value is being
removed.
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Leaving Certificate Ag. Science – Grassland
Therefore if grass is to be conserved after
cutting, all air should be removed as to
conserve the food value.
When oxygen is removed the environment
is said to be anaerobic.
In anaerobic conditions, bacteria present
cause fermentation to occur.
Fermentation is the natural conversion of
Carbohydrates to Organic Acids by
bacteria.
The presence of acids lower the pH of the
environment, to a level where the bacterial
growth and actions cease.
At this stage the environment is said to be
“pickled” or preserved.
The bacteria that is involved depends on
the amount of Carbohydrates present.
High levels of Carbohydrates allow
Lactobacillus and Streptococcus to
produce Lactic Acid in the silage.
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Leaving Certificate Ag. Science – Grassland
Low levels of carbohydrates allow
Clostridium to produce Butyric Acid.
Lactic acid silage is palatable, highly
nutritious and can be stored safely for years.
Butyric acid silage is unpalatable to stock,
less nutritious and may only last a couple of
months.
Therefore to encourage good quality silage
i.e. High Levels of Carbohydrates and the
production of Lactic Acid the farmer
should:
i. Do not cut the crop immediately after
rain – wet grass reduces carbo
concentration.
ii. Allow the crop wilt for a period of time
after cutting (1 – 2 days) – increases
Carbo concentration.
iii. Using precision chop harvesting
equipment – makes the crop more
accessible to bacterial activity.
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Leaving Certificate Ag. Science – Grassland
iv. Using a Carbo rich additive (e.g.
Molasses) - to increase the chance of
lactic acid production.
b. Silage Making Procedures
Most silage is cut from fields of permanent
grassland.
Two cuts are normal, the first in Mid – May,
and the second around July 1st.
The grass should be cut when the sward is
at its height of digestibility.
This is at the “heading out” stage, where
the DMD is 75 – 80%.
The Heading Out stage is the stage where
half of the crop are showing their seedheads
Silage may be stored in Round bales or in
Silage Pits. The procedures for cutting and
storage of silage for pits are shown below:
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Leaving Certificate Ag. Science – Grassland
1. The Grass is cut, macerated and blow
into a silage trailer using a forage
harvester.
2. The silage is transported to the pit and
heaped out.
3. An additive is used either at the pit or at
harvesting (If necessary)
4. Matted lumps of grass are removed and
the surface levelled to remove air
pockets.
5. The grass is rolled repeatedly with the
tractor to remove trapped air.
6. When sufficiently rolled the pit is
covered with at least two layers of
heavy-duty polythene.
7. This should be further covered with tyres,
manure or ground limestone, to further
seal the pit.
8. The edges of the plastic sheets are
pulled tightly and further sealed.
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Leaving Certificate Ag. Science – Grassland
9. This should be repeated 2-3 times as the
silage subsides over the coming weeks.
For round bale silage, the steps are similar
but the following is required.
1. The grass is cut and allowed to wilt for 12 days.
2. An additive is added if required.
3. A specialised machine is used to collect
the grass and make it into round bales
by covering it with plastic to remove
any air.
4. The plastic may be a wrap or a large
bag
c. Additives
Additives are used when the level of
carbohydrates is expected to be low.
There are two types of additive for silage:
a. Stimulants – are sources of sugars,
which ensure lactic acid
production. Molasses is a stimulant.
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Leaving Certificate Ag. Science – Grassland
b. Inhibitors – These are acids which
are used to lower the pH more
quickly than is natural. E.g. Sulphuric
Acid.
Molasses is used commonly by farmers on a
small scale, while acids are used by
contractors and large farmers.
d. Storage
Silage is more commonly stored in pits or
clamps.
These may be wedge clamps or run over
clamps.
These should be located on concrete as to
aid in the collection of effluent.
Clamps / pits are most effective with
sidewalls.
Without walls there is a risk of tractor
accidents and of the escape of effluent.
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Leaving Certificate Ag. Science – Grassland
The use of round bales in Ireland has
advantages but is generally more
expensive than clamp silage.
Round bale silage is used in the following
situations:
i. Silage can be made on soft, wet
land where conventional equipment
would be unsuitable.
ii. Round bales can be made on rented
land or land far away from the farm.
iii. For use where the silage is to be sold.
e. Silage effluent
Silage effluent is a by-product of the
fermentation process.
It is acidic, rich in nutrients and appears
about 2-3 weeks after the silage is sealed.
Effluent has a high BOD (Biological Oxygen
Demand), which means it can be a serious
pollutant.
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Leaving Certificate Ag. Science – Grassland
Effluent should be collected and stored in
underground pits, before being diluted and
disposed of safely.
The amount of effluent depends on the
moisture content of the silage.
After rain, huge amounts of effluent are
produced.
After wilting, very little effluent is produced.
Therefore, wilting not only ensures high
carbohydrate levels but also reduces the
level of effluent.
% Moisture at ensiling
Amount of Effluent Produced per tonne of Silage, L
85 – 90
400
80 – 84
150
75 – 79
60
< 75
0
f. Measuring Silage Quality
The following table show the parameters for
good quality silage:
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Leaving Certificate Ag. Science – Grassland
Parameter
Correct Value
Factors Affecting
pH
4
Procedures at ensiling (e.g. additive etc)
DM (%)
20
Stage of growth at cutting, wetness
DMD (%)
70 – 75
Protein
14 - 16
Stage of growth, wetness and procedures at
ensiling.
Stage of growth at cutting.
ME
10 - 11
Stage of growth at cutting, procedures at ensiling.
This can assessed very accurately in the
laboratory.
3. Hay – Making
Baled hay is a clean, conveniently handled
winter feed with very little waste.
It is very useful for farmers who wish to feed
out-wintered animals, which are far away
from the farmyard.
It does however have very little feeding
value and can prove difficult to harvest
correctly.
The following are the principles for “Good hay
making”:
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Leaving Certificate Ag. Science – Grassland
1. Cut as close to June 1 as possible to
ensure suitable drying conditions – the
field should be closed to grazing from mid
– April.
2. Cut when dry weather is expected – a hot
dry (and windy) spell is required to bring
the moisture content to 20%.
3. Use the correct machinery – Unrestricted
access to these 3 pieces of machinery
are essential:
i. Rotary Mower – can cut 1.2 – 1.5 Ha
/ hour.
ii. Power Driven Rotary Tedder – Can
work at high speeds to separate
and shake out the grass – leaves a
“fluffed up” swath of grass which
dries quickly.
iii. Baler – essential as the dried hay
must be baled and stored as
quickly as possible (from 10 Ha /
Day)
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Leaving Certificate Ag. Science – Grassland
4. Cut the crop in manageable amounts –
only cut enough that can a) be tedded
twice in a day and b) baled in a day.
5. Ted frequently to ensure fast drying –
This reduces risk of weather damage
and also maintains high Carbo levels –
reduce roughness of tedding, as the
grass gets drier.
6. Bale and remove to storage without
delay – Tedder is used to align into rows
before baling – bales should be
removed as soon as possible.
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