Leaving Certificate Ag. Science – Grassland Grasslandresources.teachnet.ie/farmnet/PDF_Files/Grassland.pdf · Leaving Certificate Ag. Science – Grassland The land is usually acidic

Leaving Certificate Ag. Science – Grassland

GGrraassssllaanndd ~~ IInnttrroodduuccttiioonn aanndd VVaarriieettiieess ~~

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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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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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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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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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* 5


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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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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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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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. 9


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. 10


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. 11


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. 12


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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GGrraassssllaanndd ~~ GGrraazziinngg MMaannaaggeemmeenntt ~~

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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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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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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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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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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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. 19


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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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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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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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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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. 24


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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GGrraassssllaanndd ~ 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).

26


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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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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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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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 seed-

heads

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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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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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 1-

2 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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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.

33


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.

34


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: 35


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 Stage of growth, wetness and procedures at ensiling.

Protein 14 - 16 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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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) 37


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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Documents

Leaving Certificate Ag. Science – Grassland Grasslandresources.teachnet.ie/farmnet/PDF_Files/Grassland.pdf · Leaving Certificate Ag. Science – Grassland The land is usually acidic