1. Leaving Certificate Agricultural Science
Introduction to Grassland
H. Jones, St. Columba’s College

2. 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.
Approximately 90% of the farmed land area in the country is devoted to grassland and is the primary resource for almost all of our agricultural output.

3. Categories of Grassland
There are three main categories of grassland.
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.
The land is usually acidic or peaty and generally stony.
It can therefore be very difficult or impossible to cultivate.

4. Categories of Grassland - 2
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.

5. Categories of Grassland
Leys
These are short term areas of grassland, sown by the farmers which display the following characteristics:
Little variability in botanical composition
High stocking rates
High levels of production.
Leys are associated with good farm practices and high levels of management and are re-sown and re-seeded regularly.

6. Grassland Distribution
Grass dominates most of the land in nearly all the counties in Ireland.
In Munster, Ulster and Connacht 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.

7. Grassland Distribution - 2
Category of Grassland
Area
(Ha, millions)
% of Agricultural
Land
Mountain / Hill Grazing
1.04
18.2
Permanent Grassland
2.93
51.3
Leys
1.24
21.7

8. Grassland Ecology
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:
Bare Soil
Grasses
Shrubs (Bramble, hawthorn and Blackthorn)
Forest species like Oak, Ash, Birch and other trees which eliminate shrubs by their shading effect.

9. Grassland Ecology - 2
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 shrubs don’t take over the area.

10. Important Grassland 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:
Hill and Mountain Grazing:
Heathers
Purple Moor grass
Bent Grasses*
Sheep’s Fescue*
Creeping Red Fescue*
Meadow Grasses*

11. Important Grassland Species - 2
Permanent Grassland:
Bent Grasses*
Fescues*
Meadow Grasses*
Cocksfoot*
Meadow Fescue*
Timothy*
Perennial Ryegrass***
White Clover**

12. Important Grassland Species - 3
Leys:
Cocksfoot*
Timothy*
Perennial Ryegrass***
Short Duration Ryegrasses***
White Clover**
Red Clover**
The asterisks determine the palatability and productivity of the species.

13. Grass Rating
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.
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.

14. Grass Rating - 2
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.
Before flowering the DMD may be 80 – 90%, and after flowering as little as 50%.

15. PRG  Very IRG  Bienniel Timothy  Poor Cocksfoot Good
Type
Productivity
Palatability
Digestibility
Persistence
PRG

Very
IRG

Bienniel
Timothy 
Poor
Cocksfoot
Good
Meadow Fescue 
Meadow Grass 
Meadow Foxtail 
Bent 

16. Perennial Ryegrass
Perennial Ryegrass is a persistent, aggressive, dominant grass.
It will take over a sward if:
Fertility Levels are high
Grazing is extensive
It is the most palatable, most digestible and most productive of the grass varieties.
It is ideal for grazing and for silage.
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.

18. Italian 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 in the first year.
In subsequent years it begins to die back.
It is a biennial.
It is ideal for early grazing or 3-4 cuts of silage.

20. Clover 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.
Very high in protein.
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.

22. Other Important Grass Species
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.
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

27. 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 the last decade, 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.

28. Seed Mixtures - 2 This gives the following advantages:
Encourages uniform growth patterns
Ensures there is always young, leafy digestible grass available as feed.
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.