Improved Grassland Management E-Book

A S Laidlaw

• Herausgeber: Crowood
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 634

Veröffentlichungsjahr: 2013

Beschreibung

This new, fully updated and revised edition of Improved Grassland Management covers all aspects of grassland management and is of particular relevance to the UK and the Republic of Ireland, although the principles discussed apply to all temperate grassland zones. Almost twenty years ago, when the original edition of this book was written by John Frame, issues such as efficiency in the use of nutrients in manures, grassland biodiversity and greenhouse gas emissions from ruminant production were either nascent, or of no relevance to mainstream grassland farming. The intervening two decades have seen the introduction of water and, latterly, air quality directives by the EU, cross compliance, the single farm payment, and an ever-increasing need for grassland farmers to be conscious of the economics of their business. The present edition, which has been thoroughly revised by Scott Laidlaw, covers the full scope of modern grassland management. Accordingly the application of technical developments in supplying and utilizing grass and forage, which remain central to grassland management, is presented in the context of these changes.Topics covered include: breeding and evaluation of new varieties of grass to meet current needs; new technology in establishing swards; legislative constraints, background science and practice in determining forage quality and the utilization of forage either for grazing or silage; feed budgeting, grassland biodiversity, grassland and climate change, and transferring knowledge and technology; wide-ranging list of sources and references, which provides the reader with further detailed information. Essential reading for all those involved in modern grassland management including grassland farmers, agricultural consultants and advisory officers, as well as agricultural, land use and biology students. Written in a reader-friendly advisory style, it can be read and understood without an in-depth technical or scientific background. Fully illustrated with 61 colour photographs.

Leseprobe

Improved Grassland Management

NEW EDITION

John Frame and A. S. Laidlaw

First published in 1992 by Farming Press

Second edition published in 2011 by The Crowood Press Ltd Ramsbury, Marlborough Wiltshire SN8 2HR

www.crowood.com

This e-book first published in 2014

© John Frame and A.S. Laidlaw 1992 and 2011

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers.

British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library.

ISBN 978 1 84797 727 4

Contents

Foreword

Preface and Acknowledgements

1 – Types of Grassland In The United Kingdom and Republic of Ireland

Area and Number of Ruminants

Sward Productivity

Survey Information

Rough Grazing

2 – Characteristics of Grasses and Legumes

Sown Grass Species

Other Sown Grass Species

Forage Legumes

Secondary Grasses

3 – Herbage Variety Evaluation

Classification of Maturity Groups

National List Varietal Evaluation

Recommended Lists

4 – Seed Mixtures

Choosing Seed Mixtures

Specimen Mixtures

Horse Paddocks

5 – Herbage Plant Breeding

Selection and Genetic Manipulation

Breeding Objectives

Forage Legume Breeding

6 – Seed Production and Certification

Seed Grades and Standards

Seed Production and Usage

Seed Growing Rules and Regulations

Management of Seed Crops

Seed Harvesting

7 – Sward Establishment and Renovation

Cultivation and Sowing

Sward Renovation

8 – Controlling Weeds

Herbicides

Docks

Thistles

Ragwort

Common Chickweed

Nettles

Annual Meadow Grass

Rushes

Soft Brome

Bracken

Gorse and Broom

9 – Effect of Soils Factors on Grass

Soil Formation

Soil Components

Soil Texture and Structure

Soil Maps

Compaction

Remedying Soil Compaction

10 – Weather, Water Control and Grass Growth

Temperature

Light

Rainfall

11 – Soil Fertility and Grass Production: Nitrogen

Response of Grass Swards to Nitrogen

Variation in Response to Nitrogen

Nitrates Directive and Nitrate Vulnerable Zones

Planning Nitrogen Fertilizer Application

12 – Soil Fertility and Grass Production: Lime and Mineral Nutrients

Nutrient Management Planning

Soil Sampling and Analysis

Lime

Phosphorus

Potassium

Sulphur

Magnesium

Sodium

Trace Elements

Blended Solid Fertilizers

Diagnosing the N, P, K and S Status of Forage Grass

13 – Using Organic Manures

Animal Slurry

Alternative Slurry Handling

Farmyard Manure

Sewage Sludge (Biosolids)

Silage Effluent

14 – Feeding Value of Grass

Concentration of Nutrients

Digestibility

Metabolizable Energy

Protein

Near Infrared Reflectance Spectroscopy (NIRS)

Intake

15 – Sward Growth and Development

Grass Tillering

Photosynthesis and Tissue Turnover

Seasonal Herbage Production

White Clover Development

16 – Components of Grazing

Defoliation

Intake

Nutrients in Excreta

Trampling

Sod Pulling

17 – Methods and Systems of Grazing

Continuous Stocking

Rotational Grazing

Grazing System and Components of Intake

Creep Grazing

‘Clean’ Grazing

Mixed Grazing

Zero Grazing

Silvopastoral Systems

Choosing a Grazing System

Grazing Systems for Hill Land

18 – Seasonal Objectives and Management

Spring Growth

Summer Management

Autumn Grass

Winter Growth and Management

Environmental Considerations in Extending the Grazing Season

19 – Silage Making

Silage in Systems

Fermentation

Respiration Losses

Wilting

Undesirable Microorganisms

Additive Use

Sealing

Silage Effluent

Aerobic Deterioration

Baled Silage

Nutritive and Feeding Value

Haylage

Health and Safety

20 – Hay Making

Stage of Growth at Cutting

Field Drying/Curing

Influence of Weather

Baling

Storage Losses

21 – Grassland Recording and Feed Budgeting

Grass Recording

Grass/Feed Budgeting

22 – Management of Forage Legumes

White Clover

Red Clover

Lucerne

Management of Legumes to Minimize N Losses

23 – Grassland and Biodiversity

Agri-environment Schemes and Biodiversity

Grassland Management for Conservation

24 – Grassland and Climate Change

Grassland’s Contribution to GHG Emissions

Grassland Management to Reduce Greenhouse Gas Emissions

Carbon Footprint

25 – Knowledge and Technology Transfer

Appendix I – Common and Latin Names of Selected Plants, Pests and Diseases

Grasses

Forage Legumes

Herbs

Hill Plants

Weeds

Pests

Diseases

Appendix II – Classification of Indices for P, K and Mg (mg/litre)

Appendix III – Key for Identification of Vegetative Grasses

Group A

Group B

Group C

Group D

Group E

Group F

Appendix IV – Seed Mixtures

Appendix V – Selected Metric Conversion Factors

Appendix VI – Sources of Data Cited and Further Reading

Index

Foreword

Globally, grassland (defined as terrestrial ecosystems dominated by herbaceous and shrub vegetation) covers some 40 per cent of the earth’s surface. In addition to its key role in sustaining ruminant livestock production, grassland has an important multifunctional role through maintaining important habitats for wildlife, reducing the effects of climate change through carbon sequestration, and providing important landscape and amenity value. Given current global increases in demand for ruminant livestock products, particularly beef and dairy products, driven by population growth and the increasing ‘Westernization’ of diets, the potential to improve the productive capacity of grassland is once again under the spotlight. This is particularly the case in those regions of the world that are less well suited to growing crops for direct human consumption, yet which are capable of supporting highly productive grass swards that can be used to generate high-quality ruminant livestock products. However, in contrast to the previous millennium, sustainable grassland systems now need to be based on ‘producing more from less’ with precise use of inputs and improved predictability of response to nutrients in both grass yield and animal output. In this context, the nitrogen-fixing ability of forage legumes will undoubtedly have a key role in the future, with reduced emphasis on fossil fuel derived nitrogen fertilizer.

In the first edition of Improved Grassland Management published almost twenty years ago, the late John Frame, an internationally renowned grassland scientist and practitioner, provided an applied scientific approach to practical aspects of grassland production and its utilization. In this substantially updated and revised second edition, Scott Laidlaw has remained faithful to John’s original approach, but has included much useful new material, including the role of grassland in biodiversity and climate change, as well as highlighting some of the important challenges of knowledge and technology transfer relating to grassland science and its application.

It is widely recognized that the full potential of grassland-based systems is rarely achieved in practice on the majority of livestock farms, in part due to the challenges of managing this complex ecosystem. A better understanding of the underlying scientific principles of grassland manage ment, as described in this book, will provide grassland farmers and their advisers with the knowledge to more fully utilize the true potential of this most adaptable and accommodating of all crops – grass.

C. S. MayneDepartmental Scientific AdviserDepartment of Agriculture andRural Development for Northern IrelandJanuary 2011

Preface and Acknowledgements

Almost twenty years ago, when the late John Frame was writing the original edition of this book, issues such as emissions from manures, grassland biodiversity and greenhouse gas emissions from ruminant production were either nascent or of no relevance to mainstream grassland farming. As a result nutrient management planning, conservation grazing and carbon footprints were treated accordingly, albeit that the value of nutrients in slurry was beginning to be appreciated in the first of those subjects. Although sward height was a recent advisory tool for grazing management, it had not been associated strongly with herbage mass estimates and feed budgeting. The first Environmentally Sensitive Areas had not long been established and were the only agri-environment scheme at that time.

The intervening two decades have seen the introduction of water and, latterly, air quality directives by the EU, cross compliance between production and environmental aspects of government support, the single farm payment, and an ever increasing need for grassland farmers to be conscious of the economics of their business. These have heightened awareness in, and the necessity to consider, these issues as fundamental to modern grassland management. Agri-environment schemes encouraging countryside management and stewardship and adoption of organic farming and sustainable grassland farming systems have also been introduced during that period.

Of course, the underpinning technical information and developments of supplying and utilizing grass and forage remain central to grassland management and so information presented some twenty years ago inevitably requires to be updated.

So Nancy Frame, John’s widow, in conjunction with The Crowood Press, asked me if I would assess whether the original edition should be updated and, if so, would I be prepared to revise it. I was honoured to be considered but I was fully aware of my limitations in lacking the breadth and depth of John’s R&D and advisory experience. However, I knew that I had the expertise and goodwill of colleagues in the Agri-Food and Biosciences Institute (AFBI) and elsewhere to draw on and so I accepted the mission.

In the original edition the focus was mainly on UK grassland farming. However, in view of the significant role played by research establishments, leading farmers and agricultural journalists in the Republic of Ireland in introducing and promoting innovations in grassland management, the scope of this edition has been widened. Other major changes include removing the chapter on hill land improvement and introducing one on grassland and climate change, introducing feed budgeting into the chapter on grassland recording and reducing emphasis on the latter. The chapter on grassland nature conservation has been rewritten so that it reflects more the objectives to increase biodiversity and the aims of countryside management agri-environment schemes.

To bring about these changes I am extremely grateful for the help I received from colleagues, either for their comments as reviewers of drafts of chapters or for discussions with them on some of the issues and details included in this edition. For comments on the drafts I wish to acknowledge Eamonn Meehan, Linda Childs, Peter Mercer, Alex Higgins, Tony Brereton, John Bailey, Peter Christie, Lynne Dawson, Andrew Dale, Gordon Tiley and Jim McAdam. I am also grateful to David Johnston, Trevor Gilliland and Peter Frost for discussion on some of the issues and technical details covered. Nevertheless, I take full responsibility for any shortcomings or omissions in the text.

Those colleagues who supplied diagrams and photographs are acknowledged in the appropriate captions.

The helpful advice of Crowood during preparation of the book (and their patience!) deserves to be recorded. I am indebted to Nancy for the opportunity to continue to be involved in John’s work, a working association that began in 1982 when we were short-term consultants together in South America and intensified with joint publication of a book and a range of papers after his retirement in 1990 until his death in November 2006.

Lastly, I wish to thank my wife, Anne, and daughter, Claire, for their understanding while they suffered from my less than undivided attention during periods of writing and for their help, especially towards completion, in word processing and proof reading.

1

Types of Grassland in the United Kingdom and Republic of Ireland

AREA AND NUMBER OF RUMINANTS

The area of agricultural land in the UK and the Republic of Ireland (RoI) is 23.9 million ha, representing 76 per cent of the total land area, and grassland (including rough grazing) makes up 16.7 million ha or about 70 per cent of the agricultural land. Grassland is the primary source of feed for ruminant livestock. As a proportion of their diet, grass and forage provide an estimated average of 50 to 60 per cent for dairy cows, 80 to 85 per cent for beef cattle and 90 to 95 per cent for sheep. Due to differences in systems of production within an enterprise type, these averages conceal wide ranges. Total livestock numbers comprise 17 million cattle and 38 million sheep (see Table 1).

Table 1: Ruminant Numbers in the UK and Republic of Ireland (Million)

Figure 1 shows the pattern of agricultural land use in both countries. In the UK the grassland area is divided into three categories: under five years old, over five years old and rough grazing. Grassland under five years old (1.1 million ha) includes newly sown swards and a range of swards from one to four years old. Some of these may have been deliberately sown to last only for up to four years; others may be in the early years of an intended longer duration.

Short term leys are based on Italian, hybrid and perennial ryegrasses (see Appendix I for Latin names of plants). Where seed mixtures are intended for medium or long term duration, perennial ryegrass is the dominant constituent, often with the addition of other grasses, especially timothy, and including white clover. Seed mixtures are discussed fully in Chapter 4.

In the UK, grassland over five years old (6 million ha) includes temporary grassland or leys that may be part of an arable grass rotation, possibly up to ten or more years, and also permanent grassland, which is old grassland that may have originally been sown or simply have been derived by management. The statistics do not indicate whether or not the grassland in the two age categories is part of a rotation with arable crops or land that will always be grassland. In independent grassland surveys, this latter category is regarded as permanent grassland regardless of its age at the time the survey information is recorded; the terms ‘permanent grassland’ and ‘old grass’ have also been used to categorize grassland over twenty years old.

Figure 1: (A) Agricultural land use in the UK and Republic of Ireland; (B) and (C) Classification of grassland and rough grazing in the UK and Republic of Ireland, respectively.

Source: DEFRA; O’Mara

The third category – rough grazing – comprises 5.6 million ha, made up of 4.4 million ha of sole right and 1.2 million ha of common rough grazing. Usually unfenced and subject for many years to an extensive type of management, rough grazing is equivalent to open rangeland in many countries.

In the RoI national statistics do not take account of the age of grassland but grassland is separated into the area under pasture (2.2 million ha) and that used for grass silage (1.0 million ha) and hay (0.2 million ha). These are not mutually exclusive as particularly silage and hay areas may be grazed at some time in the year, especially during the second half of the growing season. Rough grazing accounts for a further 0.5 million ha.

The percentage of agricultural land under grass increases broadly from east to west. This is the result of increasing rainfall, a generally decreasing soil fertility and the difficulties of arable cropping. Grassland farming is also predominant at higher altitudes, with an increase in rough grazing and a reduction in length of growing season on account of lower temperatures and poorer growing conditions. Much of the rough grazing – 4 million ha – occurs on the hills and uplands of Scotland, with much of the remainder in the Pennines of northern England, the mountain ranges in the west of Ireland and mountains of Wales.

SWARD PRODUCTIVITY

The potential production of grass swards has been calculated to be 27 to 30 tonnes/ha of herbage dry matter (DM). Production within this range has been achieved in very small experimental plots when water and nutrients were not limiting. In experimental plots of 5m2 and upwards, production of 18 to 21 tonnes/ha DM is more commonly obtained under high fertilizer nitrogen (N) use and infrequent cutting, which simulates conservation. Under more frequent defoliation, to simulate grazing, yields are usually 11 to 13 tonnes/ha DM although yields in excess of 15 tonnes/ha DM are commonly reached in the south of the RoI. In farm practice, herbage production is very variable and well-recorded estimates are scarce, but maximum on-farm production is in the range 12 to 15 tonnes/ha DM. However, as grassland receives on average less than 100kg N/ha, and much of the grassland area is permanent pasture or old leys, actual dry matter production is within the range 5 to 7 tonnes/ha DM. In grazed grassland, not all of the grass available to the animal is grazed, 80 per cent being a high utilization efficiency, so average yield of utilized grazed grassland is 4 to less than 6 tonnes/ha DM. This contrasts greatly with the much higher potential assessed in plots.

For grass/white clover swards, a potential of 18 to 22 tonnes DM has been calculated. Production as high as 15 tonnes/ha has been achieved in experiments, but annual yields of 8 to 10 tonnes/ha are more common, and on farms yields of 6 to 8 tonnes/ha would be the norm. However, production is very dependent on the content of clover, which fluctuates widely in practice, especially where the swards have not been managed to favour clover.

Table 2: Percentage of Agricultural Land in Each Grade of Agricultural Land Classification

In the UK agricultural land grade is graded by quality or potential. A set of physical criteria including altitude, gradient, climate, soil and drainage, and the extent to which these factors constrain agricultural usage, are applied on a scale from 1 (highest quality) to 5 (see Table 2).

Grades 1 and 2 have few limitations for agricultural use, other than perhaps minor soil or drainage problems; such land is often under intensive arable cropping and horticulture. Grade 3 has moderate soil or even climatic limitations and forms a core of good arable land for flexible cropping and lowland grassland. Hills and uplands are mostly in grades 4 and 5 and are regarded mainly as suitable for sheep and cattle rearing. Grade 4, largely upland and permanent grassland, and grade 5, mainly rough grazing and limited areas suitable for improvement, have severe soil climatic and altitude constraints. Some of the mountainous slopes and peaks can support only very poor rough grazing of sheep’s fescue, bilberry, mosses, lichens and bog plants.

About 80 per cent of Scotland and Wales is in grades 4 and 5 in a ratio (grade 4:grade 5) of 1:7 in Scotland and 1:0.8 in Wales. England has lower proportions of grades 4 and 5 land (26 per cent) and a ratio of 1:0.7, while in Northern Ireland, with 55 per cent grade 4 and 5 land, the ratio is 1:0.1. As Table 2 indicates, 52 per cent of UK land has been classed as grades 4 and 5, an area equated closely with the less favoured areas, comprising 9.8 million ha, specified by the EU.

Agricultural land in the RoI is graded slightly differently. Soil type is the main criterion with degree of difficulty in usage superimposed on type (see Table 3).

More than half the agricultural area is in the moderately good and good classes (either dry mineral or wet mineral caused by high water table, seep or spring problems), while the remainder are either wet impermeable mineral soils, peats or mountain or hill soils. Broadly, the approximate 50:50 divide between classes 1–3 and 4 and 5 in the UK system in Northern Ireland is similar to the division between moderately good/good and difficult or marginal in the RoI classification.

Table 3: Proportion of Soils in Major Land Classes in the Republic of Ireland

SURVEY INFORMATION

As structured grassland surveys have not been carried out in the UK and the RoI in recent decades, information is somewhat dated. Nevertheless, the basic principles associating grassland type and composition established from these surveys still apply today.

A major survey conducted on the permanent grasslands of England and Wales, published in 1980, showed that the presence of preferred species (mainly perennial ryegrass, timothy and white clover) declined steadily with age of the sward and that non-preferred indigenous grasses increased (see Table 4).

Table 4: Average Content of Preferred Species in Permanent Grassland of Differing Ages on Contrasting Farm Types (Percentage Contribution to Ground Cover)

Meadow grasses were more frequent in the younger age group while bent grasses, Yorkshire fog and fine leaved fescues increased in the older swards. Soft brome grass, which is an invasive weed grass, was abundant in frequently mown fields; docks occurred more frequently in younger than older swards, while the converse was true for creeping thistle and buttercups. A ‘good’ clover content, mainly white clover defined as well distributed and contributing more than 5 per cent ground cover, was more common in the younger swards and on beef rather than dairy farms (see Table 5).

Table 5: Proportion of Swards with a Good Content of Clover in Permanent Grassland of Differing Ages on Contrasting Farm Types (Percentage of Farms in Each Group)

A survey of permanent swards in England and Wales, in which 85 per cent of the land was above 120m altitude, gave similar results to the survey of lowland permanent grassland (see Table 6). It was also noted that perennial ryegrass, the dominant sown grass, was most abundant in swards receiving high fertilizer N inputs, particularly at lower altitudes and where mown rather than grazed, for example 16 per cent at nil N compared with 58 per cent where over 300kg N/ha were applied. A good contribution of white clover, defined as 10 per cent or more of ground cover, was associated with low N inputs, good drainage and grazed swards. Unsown fine leaved fescues, especially red fescue, increased with sward age, particularly where no fertilizer N was applied.

Table 6: Average Botanical Composition of Upland Permanent Grassland of Different Ages in England and Wales (Percentage of Total Ground Cover)

Another survey examined grassland on ‘stock rearing with arable’ farms in eastern Scotland (see Table 7). Two-thirds of the grass was rotational, under seven years old, and 30 per cent was ten or more years old. Species contribution was recorded on a herbage cover basis, bare ground being excluded. Sown-species content fell with age to 49 per cent in the oldest swards. Perennial ryegrass was the main sown constituent present, followed by cocksfoot and timothy. Half of all fields surveyed had under 15 per cent of white clover. Bent grasses, Yorkshire fog, meadow grasses and fescues were the main unsown grasses present.

Table 7: Average Content of Sown Species in Rotational Grassland of Differing Ages on Stock Rearing Farms (Percentage Contribution to Total Herbage Cover)

Sward Age (Years)

Sown Species (%)

1-2

93

3-4

86

5-6

83

7-9

74

10-20

66

Over 20

49

All ages

77

Source: Forbes et al.

ROUGH GRAZING

Rough grazing is a generic name for semi-natural plant communities that have evolved under a host of influencing factors. Soil type and prevailing climate are predominant but the influence of man is over-riding In the uplands, most areas below the tree line, which varies with the exposure of the land, were originally wooded. Except in a few surviving remnants and in modern afforestation, woodland has been unable to regenerate after clearance because of grazing and burning. The grazing management is generally extensive and open range and the sward species are resistant to grazing and burning. Purple moor grass, for example, with its well-protected growing points, thrives under burning every three to five years. Heather requires more infrequent burning, every eight to fifteen years, if it is to flourish. If overgrazed, especially by sheep, heather is succeeded by grass heaths with vegetation related to the inherent land quality.

Plant communities are often dominated by only a few species. The growing season is short and highly seasonal with late spring flushes. Some of the subsidiary species are valuable at specific times of the year, when they become acceptable to stock either because of their stage of growth or because there is nothing else to graze. Sedges, heath rush and cotton grass all have grazing value in early spring, for instance, but they are neglected at other times of the year. Some species are rich in specific minerals; for example, young purple moor grass and cotton grass have high phosphorus contents while bilberry is rich in calcium. Variation in production capacity among vegetation types can be as high as twentyfold.

Due to the value of these semi-natural communities to biodiversity and landscape, their management may be included in agri-environment schemes, or some are designated as protected areas. This is covered in more detail in Chapter 23.

2

Characteristics ofGrasses andLegumes

Next in importance to the profusion of water, light and air, those three great physical facts which render existence possible, may be reckoned the universal beneficence of grass.

J.J. Ingalls (1872)

Although temperate grasses share many features in common, especially their general form, they differ widely in their responses to soil conditions and other environmental variables. As pointed out in Chapter 1, botanical composition of sown swards changes with age. Although many factors influence the relative competitiveness of species some are more important than others. The most important within a climatic zone, after management, are mainly soil-based.

Main factors that influence sward composition:

• Type of management

• Nutrient availability

• Soil moisture

• Soil pH.

Source: Peeters

This chapter provides information on the main sown and natural grass species in lowland, particularly with regard to their agronomic characteristics and their response to some of the factors listed above.

SOWN GRASS SPECIES

Perennial Ryegrass

This is clearly the most important and widely used grass species in seed mixtures, exhibiting rapid establishment, good tillering ability, excellent production response to fertilizer N and high acceptability to stock. At equivalent growth stages to other species, both perennial and Italian ryegrasses produce higher DM yields at specific levels of digestibility. Production of perennial ryegrass at a given level of digestibility can be at least 20 per cent more than that of cocksfoot, for example. However, more recently bred varieties of other sown species suggest that the gap is narrowing.

Inflorescences of perennial ryegrass.

Perennial ryegrass is persistent if soil fertility is high, particularly the intermediate and late heading varieties. It is also tolerant of intensive grazing and of cutting, provided interval between defoliations is not excessively long. It regrows quickly after defoliation provided swards are not cut for repeated heavy crops of silage or for hay at a mature stage of growth, since these managements reduce tiller density.

There are numerous recommended varieties and seed is normally readily available, except perhaps the most recently recommended varieties. As the varieties exhibit a wide range of characteristics, for example in heading dates, earliness of growth, disease resistance and persistency, perennial ryegrass can fulfil the needs of most farming systems. It is also an important grass in other temperate regions of the world, such as New Zealand.

However, perennial ryegrass does not grow well under very dry conditions, where summers are hot or on infertile soils. When grown under infertile conditions the sward becomes weak and stemmy, lacking longevity and susceptible to invasion by indigenous grasses and weeds. Its susceptibility to winter damage during cold periods or frost damage on first spring growth has been greatly reduced due to progressive improvement in cold hardiness of varieties and less frequent occurrence of cold winters in recent years.

Distinctive varieties of the different ryegrass species have been bred with double the number of chromosomes of normal diploid varieties. These commercial tetraploid ryegrasses were introduced in the 1960s. Tetraploidy can also occur as ‘sports’ in natural populations. Some of these were developed, and cocksfoot grass and white clover, for example, are natural tetraploids. Timothy is a hexaploid, that is it has six sets of chromosomes.

Perennial ryegrass (left) and red fescue tillers. Leaves of red fescue are thin and bristle-like.

Perennial ryegrass cultivars are either diploid (natural number of chromosomes) or tetraploid (double the natural number of chromosomes). Plant breeders induce tetraploidy in ryegrasses by chemical, radiation or other treatment and they follow this by selection programmes. Compared with diploids, tetraploids have larger seed (two to four times heavier than corresponding diploids). Originally, tetraploids had a lower population density, larger tillers, higher water-soluble carbohydrate content, higher digestibility, lower dry matter content and higher dry matter yield than diploids. Some of these attributes conferred higher animal intake characteristics on tetraploids. However, the differences are now not so clear-cut as some tetraploids have relatively high tiller densities and some diploids have, for example, high dry matter yield potential, high water-soluble carbohydrate content and elevated digestibility. The high moisture content (low dry matter) of tetraploids is often cited as a disadvantage in silage or hay making, where wilting and drying are required, but in fact the differences are small in comparison to fluctuations brought about by nitrogen fertilization. The openness of most tetraploid ryegrass swards compared with diploid swards makes them compatible with clover.

To identify perennial ryegrass in a vegetative sward in the field, it is one of only two species whose tiller has a red base and shiny underside to its leaves. The other is red fescue, but its leaves are generally bristle-like.

Italian Ryegrass

This is the second most popular grass species sown, although its popularity has declined with the increasing trend towards long-term swards and greater use of the longer living hybrid ryegrasses. It is a biennial, that is it usually completes its lifecycle in two years, although some crops produce reasonable yields in their third year. It is most productive in the first full year after sowing.

Part of an Italian ryegrass inflorescence (right), showing awns (bristles) on the florets within its spikelets (i.e. structure comprising groups of florets), compared with the bristleless spikelets of perennial ryegrass (left).

Italian ryegrass commences growth early in spring, especially if sown in late summer rather than in spring the previous year. Under intensive fertilizing and cutting for conservation it gives good production of herbage of high digestibility. It can be grazed before cutting for silage since it is not an early heading grass, most varieties heading during the same period as intermediate perennial ryegrass. It is also productive in the year of sowing if sown in spring because of its rapid establishment and growth vigour. It can therefore be used as a catch crop or as a pioneer constituent in mixtures with forage rape.

The main drawback with Italian ryegrass is its short-lived nature, which is associated with a high degree of stem production; this lowers acceptability to grazing stock in midsummer if swards are not well grazed. Production from the second full harvest year is also substantially lower than in the first. Older swards of Italian ryegrass or swards that are allowed to enter winter with surplus growth are more susceptible to winter damage than other main sown species. In Recommended Lists Italian ryegrass varieties are rated lower for winter hardiness than perennial ryegrass varieties.

Hybrid Ryegrass

This is a bred hybrid between Italian and perennial ryegrass, with the aim of incorporating the more desirable characteristics of both parents, for example the rapid establishment and vigour of Italian ryegrass with the tillering ability of perennial ryegrass. Hybrids may resemble one or other of the parents or be intermediate in appearance. The Italian types have awned seedheads, form an open sward due to a low tiller density, give good spring growth and have higher yields than the perennial types. The majority of hybrids on Recommended Lists are tetraploids and the best hybrid ryegrasses are less productive than the best Italian ryegrasses but exhibit better ground cover and drought tolerance. The perennial types can potentially remain relatively productive for up to five years. Their main role is in high production swards that are mainly intended for silage production but they are not restricted to only-cutting swards. In grazed swards, their midseason acceptability is usually higher than that of Italian ryegrass.

Westerwolds Ryegrass

This is a rapidly establishing annual species (considered an annual form of Italian ryegrass) that gives high production in the season of sowing if seeded early and adequate moisture is available. It is therefore suitable for routine or emergency catch cropping. Both diploid and tetraploid varieties are available. Unlike Italian ryegrass, it heads profusely in the sowing year so defoliation, whether by cutting or grazing, must be sufficiently frequent to keep swards leafy to prevent a decline in their digestibility with maturity.

OTHER SOWN GRASS SPECIES

Timothy

This species occurs naturally as a hexaploid (six sets of chromosomes in its nucleus). It is better suited to cutting than grazing but it is very acceptable to grazing animals and, when mixed with competitive grasses such as perennial ryegrass, its slow regrowth leads to its being grazed out if grazing is intensive. It is useful for the cool wet conditions in the north and west and is invaluable on wet, peaty and heavy textured soils. Being the most winter hardy of the main grass species and also winter green, it produces valuable early growth in upland areas where it tolerates lower fertility than ryegrass. The seed is very small, 2 to 3 million per kg, slow to establish and should not be sown deeper than 10 to 15mm.

Timothy herbage has a low mineral content. Its digestibility declines less rapidly with maturity than the other major grasses, though the decline starts at an earlier growth stage. Therefore, it should be cut well before ear emergence if high quality forage is required, since the mature herbage is very stemmy and extremely low in digestibility and crude protein content. It continues to be a minor component in many seed mixtures designed for grazing and specialist mixtures, for example for hay or haylage for horses.

Inflorescences of timothy.

Inflorescence of cocksfoot.

Cocksfoot

The main reason for sowing cocksfoot is for its drought tolerance and, although a relatively minor species, it is valuable on light-textured soils in dry areas.

In general purpose mixtures it can provide useful early season and autumn production in upland areas. It is slow to establish and in older grassland it is conspicuous in swards due to a coarse tufted habit of growth, notably if the sward is understocked, so management is difficult as it has to be kept in a leafy state. The older varieties had a low water-soluble carbohydrate content and relatively low production capability making them unsuitable for silage making. Some varieties bred in recent years are more suited to intensive grassland production, than the older coarser varieties, being less tussocky and having higher water-soluble carbohydrate contents and hence higher digestibility.

Meadow Fescue

This grass species grows best under cool, moist conditions tolerating wet, even occasionally flooded soils, and is highly acceptable to grazing stock when kept leafy. Being slow to establish and non-aggressive, it contributes little in mixture with vigorous species such as perennial ryegrass.

It was used in timothy/meadow fescue/white clover mixtures in the past because of its compatibility with clover, and also in hay mixtures, but weed ingress was sometimes a major problem.

Increased fertilizer N use and stocking rates have diminished the role of meadow fescue as it does not respond well to high N rates and lacks persistency under intensive stocking. Varietal choice is limited and it is now a minor species. Nevertheless, with lower N fertilizer rates and stocking rates likely to become more prevalent, there may be a revival in meadow fescue’s role in seed mixtures.

A typical fescue inflorescence.

Tall Fescue

This is a very adaptable species, growing well in dry or wet conditions; it is also very winter hardy. Established tall fescue swards grow earlier in spring than Italian ryegrass, are very responsive to fertilizer N and have the potential for high production. Tall fescue can withstand frequent mowing producing a consistent supply of herbage over the growing season as required for industrial processes such as production of dried grass pellets. It has several major drawbacks, however, being slow to establish, of poor acceptability to grazing animals, and of lower digestibility than the other main grass species. Varietal choice is also limited. While little used in maritime north-west Europe, it is an important species in a few drier areas of Europe and some other regions of the world, for example, in the southern United States of America and Argentina.

Prairie Grass

This minor grass, a species of brome grass, performs best in dry conditions and grows well in autumn. It gives very high production on free-draining soils under mild southern England conditions where its susceptibility to frost is less of a problem than in northern conditions. Its digestibility is better than timothy or cocksfoot but not the ryegrasses.

As it produces an open sward with an upright growth habit it is more suited to cutting for conservation and rotational grazing than for continuous stocking. As its carbohydrate reserves are less densely confined to the base of the tiller, its optimum cutting height is about 6cm, compared with the 3–4cm for perennial ryegrass. Also its optimum cutting interval is longer than perennial ryegrass (about four leaf appearance intervals compared to about three leaf appearance intervals for perennial ryegrass). In New Zealand, where it is a recognized drought-resistant species, swards have been rejuvenated by temporary cessation of grazing to allow seed head development and natural reseeding. It is a very large awned seed with a 1,000 seed weight of about 13g, compared with 1.5 to 3.5g for perennial ryegrasses.

Sweet Brome

This very minor species with similar attributes to prairie grass may have a limited role for conservation on light sandy soils in dry areas. It has shown some compatibility with forage legumes since it develops an open sward. It is unlikely to be suitable for widespread use due to its variable performance compared with other grasses.

FORAGE LEGUMES

The importance of leguminous plants lies in their rhizobial N-fixation ability, soil improvement properties and their excellent feeding value for animal production. These advantages, having been neglected in much of Europe during the era of heavy fertilizer N use, are beginning to be appreciated again for economic reasons and the growing interest in sustainable production systems. Forage legumes are only briefly discussed here since more detailed information can be found in Chapter 22. White clover is by far the most important forage legume used in Britain, followed by red clover and then lucerne. Other species used occasionally include sainfoin and birdsfoot trefoil.

White Clover

White clover is a perennial legume that spreads through the sward by branching stolons. Finely rooted daughter plants develop from nodes on the stolons, eventually taking the place of the tap rooted mother plant, which dies out. The amount of clover production is thus related to the amount of stolon present. The N-fixing bacteria of the root nodules produce most of the N needed by white clover and the N-rich material is gradually released into the soil by leakage, decomposition and turnover of senescent material. This released N can be taken up by the associated grasses. In comparison with grass, clover is richer in protein and minerals but lower in fibre. It maintains a better digestibility over the season, is more acceptable to stock, and the digested nutrients are metabolized more efficiently. While best suited as a grazing plant, it can also be successfully cropped for high quality silage.

Inflorescence of white clover.

There is a potential risk of cattle bloating on clover-rich swards. While clearly a factor to be borne in mind, its perception as a problem is often greater than it actually turns out to be. Experience from grazing trials and from those farms making significant use of white clover has so far not indicated bloat as a major problem. However, various preventative and remedial measures are available.

Red Clover

Red clover is primarily a plant for cutting rather than grazing, having an upright growth habit and with the shoots developing from a plant crown. Its use in general-purpose seed mixtures has declined, but it can be used in special purpose, clover-dominant mixtures for silage. It is the principal source of nitrogen, other than organic manures, in silage swards on many organic farms. Although clover rot from the fungus Sclerotinia trifoliorum and damage from the stem eelworm (Ditylenchus dipsaci) are limiting factors, resistant varieties are available. The main disadvantage of red clover is its lack of longevity, which does not fit well with the increasing use of long-duration swards for animal production.

Inflorescence of red clover.

Alsike Clover

Alsike clover has an upright growth habit, similar to red clover, with a pink flower. It is tolerant of wet and acidic conditions. It was grown more widely when complex grass seed mixtures were normally sown and if sown nowadays it is usually as the minor component of a mixture. It was common in seed mixtures when hill land was reseeded due to its relatively high tolerance to adverse soil conditions. Its life cycle is similar to that of red clover, that is, it is at its most productive in the first two years after sowing.

Inflorescences of alsike clover.

Lucerne

Lucerne is a special-purpose plant primarily suited for conservation. It will produce well for three or four years under the better soil and climatic conditions found in southern Britain. It has a deep tap root requiring freedraining soil, high pH and adequate fertility for longevity. Varietal choice is limited but resistance to Verticillium wilt and to stem eelworm are necessary for it to be grown successfully. Rhizobial inoculation of the seed is essential when sown in fields in which it has not been grown previously.

Sainfoin

This minor perennial legume has similar attributes and agronomic requirements to lucerne, but with 20 to 30 per cent lower production. There have been no intensive breeding programmes, though several strains or eco-types are available. The common or single-cut type is more persistent than the giant or double-cut type. The seed is best direct sown in spring at 50kg/ha for milled seed, that is without the seed coat, and at double this rate for unmilled seed, perhaps mixed with a non-aggressive companion grass such as meadow fescue at a low seeding rate. It does not appear to have any serious disease or pest problems, and is essentially a plant for cutting, but the aftermath can be grazed. The protein rich forage is highly acceptable to stock and is of high nutritive value. The tannins in the forage limit degradation of the plant protein in the rumen. This improves the efficiency of protein use, since this protein can then be utilized more efficiently later in the digestive tract giving sainfoin a valuable bloat-free characteristic.

Inflorescence of birdsfoot trefoil.

Birdsfoot Trefoil

This species occurs naturally and widely in herb-rich hill and lowland swards, but is rarely sown in Britain. It is used in Canada and the northeastern United States of America, for example, where it is adapted to the humid conditions.

It is more tolerant of lower levels of soil pH than white clover and has a potential place on soils where clover does not thrive. If sown in mixtures, a non-aggressive grass companion is required. The important trefoil varieties available vary in their tolerance to cutting and to grazing so the proposed use will determine varietal choice. Because of a high tannin content, birds-foot trefoil does not cause bloat in cattle. The related species, marsh birdsfoot trefoil, has shown potential in wetlands but there are specific establishment and management needs. It has an extensive rhizome system, the development of which is a major key to persistence. It is used for wetland pastures in New Zealand and Australia and with agroforestry swards.

SECONDARY GRASSES

Surveys have shown that many types of grassland, especially long-term or permanent grassland, contain unsown species. These have variously been called natural, secondary, undesirable, non-preferred or even weed grasses. Bent grasses, fine-leaved fescues, Yorkshire fog, smooth- and rough-stalked meadow grasses, meadow foxtail, crested dogstail and sweet vernal are the most commonly found. A survey of permanent grassland in England and Wales, for example, showed that bent grasses occupied at least 25 per cent ground cover in 8 per cent of one- to four-year-old swards, increasing progressively to 57 per cent of swards more than twenty years old (see Chapter 1).

A predominantly ryegrass sward is the normal aim in grassland improvement but, as discussed above, this species has a requirement for generally high fertility conditions and controlled management. Several secondary grass species are adapted to withstand or even exploit adverse soil, climatic and management conditions. Soil fertility surveys have shown that lowland fields are often deficient in lime, phosphorus or potassium so it is fortunate that there are grasses that can exploit these poorer soil environments and tolerate adverse grazing practices. Bent/fescue associations are the best of the indigenous upland swards, often with crested dogstail, Yorkshire fog and sweet vernal interspersed. As noted earlier, bent grasses are also abundant in old lowland pastures.

In the past there have been advocates for the breeding of varieties of some of the secondary grasses for agricultural use. However, the prevailing argument against such a programme has been the lack of a potential market. The area of grassland resown, especially in marginal land, is declining and improvement in persistence of varieties of currently bred species continues, so it is highly unlikely that varieties of these secondary species are to be bred for agricultural use. Of course, improved European varieties of secondary species are bred for sports turf and amenity purposes, and it is possible that agricultural evaluation may identify one or two of these from the fescues or meadow grasses, albeit as a bonus to grassland farming and not as an objective.

The productivity and potential of secondary grasses were investigated at Ayr, Scotland, using different fertilizer N rates, cutting managements and swards, with and without white clover, all compared with perennial ryegrass (see Figure 2). Some grasses, notably Yorkshire fog, red fescue and creeping bent grass, were superior in herbage DM output to perennial ryegrass at low or moderate N rates (0 and 120kg N/ha/year) but this superiority was not sustained as N rate increased. Nevertheless, Yorkshire fog, red fescue and smooth-stalked meadow grass still gave high DM production at higher rates of N (360 and 480kg N/ha/year). Crested dogstail and sweet vernal gave higher output than ryegrass only at nil N. The least productive grass was common bent.

However, the superiority of ryegrass in digestibility (D value) was unchallenged at all N levels. Consequently, in yield of digestible herbage, ryegrass was preeminent at all N rates save nil N, where only Yorkshire fog and S59 red fescue performed better. Next to ryegrass in digestibility were Yorkshire fog and crested dogstail. Red fescue, bent grass and smooth-stalked meadow grass were consistently low in digestibility. The lowest crude protein contents were associated with ryegrass and the most productive secondary grasses. Phosphorus, potassium and calcium contents were satisfactory for grazing stock in all the grasses, but magnesium levels were marginal.

Yorkshire fog, red fescue and sweet vernal were found to be more productive than ryegrass at nil N at the first (May) harvest. As N level increased, Yorkshire fog, red fescue and bent grass maintained a similar advantage over ryegrass. The same grasses outperformed ryegrass in midseason (June, July, August) at nil and 120kg N/ha/year but the advantage switched to ryegrass at higher N rates. Later in the season, Yorkshire fog, red fescue and creeping bent grass out-produced or matched ryegrass DM yields at all N rates.

Figure 2: Mean annual DM production over three harvest years at each fertilizer N rate (perennial ryegrass cv. Perma and a range of secondary grass species).

Source: Frame.

In other work, red fescue, smooth-stalked meadow grass and crested dogstail proved to be compatible with white clover and therefore have potential for use in grass/clover swards, possibly by the introduction of clover into swards dominated by these species, even if seeds of these species were not available for mixtures. The close-knit sward developed by Yorkshire fog and creeping bent was not conducive to clover stolon proliferation and development of clover growing points.

The above findings have been reinforced from English and Welsh sites, comparing permanent grass swards of mixed composition with reseeded perennial ryegrass. A range of fertilizer N rates was used and the sites covered a variety of environmental conditions. The permanent grassland was less productive than reseeded perennial ryegrass the first harvest year, partly because of extra N being available to the ryegrass swards from mineralization in the soil resulting from cultivation. However, the advantage of the reseeded swards was only maintained in later harvest years at high rates of fertilizer N application – above 300kg N/ha/year (see Figure 3).

These results indicate that certain secondary grasses and some permanent swards can match or outperform perennial ryegrass production at nil to moderate N application rates. It is apparent that some can also respond to high soil fertility and would repay increased N inputs on the farm. A few secondary grasses have a production advantage over ryegrass at certain times of the year, which is a feature worth exploiting. Some fall down on their digestibility, but are not lacking in minerals essential for stock health.

Figure 3: Herbage DM yields at a range of nitrogen fertilizer levels from permanent swards (–––) and reseeded perennial ryegrass (——) averaged over 16 sites cut at 4-weekly intervals: (A) 3-year mean and (B) 4-year mean, including establishment phase.

Source: Hopkins et al.

It can be concluded that it is not always essential to reseed swards because they do not contain a good proportion of primary grasses, especially bearing in mind reseeding costs and temporary loss of production during establishment. Performance and response to better management should be assessed first. Reseeding to a perennial ryegrass-dominant sward is thus not always warranted, particularly if the sward is to receive low to moderate N inputs.

The chief characteristics of selected secondary grasses are outlined below.

Red Fescue

Red fescue is suitable for inclusion in seed mixtures for land reclamation under harsh hill and upland environments and for infertile soils, because of good winter hardiness, winter greenness and sward density. Its main drawback is low digestibility and poor mineral concentrations. It is not highly acceptable to grazing animals because of its hard, needle-like leaves and early flowering habit if not well grazed. Many varieties have been bred for amenity grassland and sports turf, but few for agricultural grassland where it would be advantageous if its nutritive value was improved.

These inflorescences of creeping bent are typical of bents generally.

Bent Grasses

Bents are adapted to environments of low potential production. They can take up increased fertilizer N but are unable to metabolize the N for high DM production; they may therefore be rich in crude protein if soil fertility is high. They are generally of low digestibility, although high in mineral concentrations. Many varieties have been bred for amenity grassland but few have been tested for agriculture.

Smooth-Stalked Meadow Grass

Dry matter yield of smooth-stalked meadow grass (also known as Kentucky bluegrass) responds well to fertilizer N so it has production potential and an ability to increase its proportion in the sward with increasing soil fertility. It is also highly acceptable to stock. It is included in seed mixtures for dry areas due to its drought resistance. Its disadvantages include poor digestibility and poor establishment. Many amenity cultivars are available. It is used as a sown grass in some Nordic countries.

Inflorescences of annual meadow grass, typical of all meadow grasses (including rough-stalked and smooth-stalked meadow grass).

Yorkshire fog inflorescences at different stages of development after emergence.

Yorkshire Fog

This grass has high production potential but its acceptability to stock reduces its rating. Some breeding effort has gone into it in New Zealand where there is a named variety, Massey Bastyn. British trials show Yorkshire fog to be productive at both low and moderately high rates of fertilizer N, with good digestibility and mineral concentrations. Its acceptability to stock is increased if it is kept at a leafy stage. It is prone to winter damage.

Meadow Foxtail

This species is one of the earliest to flower in spring.

Inflorescence of meadow foxtail. Note the similarity to timothy, but timothy does not have fine bristles (awns) on the florets within its spikelets.

Crested Dogstail

This species has poor production capacity poor response to applied N and a propensity to produce stem. A variety bred in New Zealand is available. While crested dogstail has shown compatibility with white clover, there are better compatible grass species available.

Inflorescence of crested dogstail.

Sweet Vernal

Overall this species has few advantages for agricultural grassland although it can produce early in the season, and is relatively productive at low soil fertility. It has poor concentrations of minerals.

Inflorescence of sweet vernal.

Rough-Stalked Meadow Grass

This species has given poor performance in Scottish trials, persisting only for one harvest year, although herbage quality was satisfactory. Even bred varieties from Denmark did not persist. The presence of rough-stalked meadow grass in some swards should be regarded as undesirable, although it may have some use in the reclamation of wet soils.

3

Herbage Variety Evaluation

But of all sorts of vegetation the grasses seem to be most neglected; neither the farmer nor the grazier seems to distinguish the annual from the perennial, the hardy from the tender, nor the succulent and nutritive from the dry and juiceless.

Gilbert White, The Natural History of Selborne (1788)

As the UK and RoI are members of the European Union and signatories to the Union for the Protection of Varieties, a variety marketed in an EU country needs to be on the EU Common Catalogue of varieties. This is an amalgamation of varieties on the National List of each member country. To qualify for entry to the National List of a country a variety needs to have been evaluated for distinctness, uniformity and stability (DUS tests). So it must be distinct from all other approved varieties, variation from individual to individual should be within a predetermined range (that is, the variety should be uniform), and characteristics should be stable from generation to generation. A candidate variety also needs be evaluated for its value for cultivation and use (VCU) to be considered for entry to the National List. England, Wales, Scotland, Northern Ireland and the RoI each has a recommended list of varieties so further evaluation is required to qualify for inclusion on these lists.

CLASSIFICATION OF MATURITY GROUPS

Varieties of forage grasses are classified according to their heading date with dates and groups specific to each species. So although varieties of perennial ryegrass and timothy are divided into early (E), intermediate (I) and late heading (L) groups, the date of division between groups differs for the two species. For example, early heading timothy varieties head three weeks or more later than early heading perennial ryegrass varieties. Heading date of the earliest and latest heading variety within perennial ryegrass can differ by more than six weeks, from early May to mid-June. Heading date in Italian ryegrass varieties is generally within the range equivalent to intermediate heading perennial ryegrasses. Only two groups, E and L, are assigned for cocksfoot, while meadow fescue is divided into three heading groups. The number of varieties commercially available in the latter two species is very small. Westerwolds ryegrass has a profusion of heads in the seeding year when sown in spring but there are only small differences between varieties in ear emergence patterns.

Figure 4: Relationship between the average leaf area of a variety and ground cover as a measure of persistency under a range of grazing managements.

Source: Gilliland

White clover varieties are classified by leaflet size, measured as length × breadth of the middle trifoliate leaflet in mm2. There are four groups: small (S), medium (M), large (L) and very large (VL), with most varieties falling into the first three categories. There is a good correlation between leaflet size and persistency under grazing or frequent cutting (see Figure 4), the smaller leaved varieties being more suitable for severe defoliation – typical of sheep grazing – and the larger leaved varieties more suitable for cattle grazing or silage cutting.

Red clover varieties are either early or late flowering, the range of flowering dates spreading over five weeks. All the lucerne varieties currently used in the UK are in a single maturity group, and flower within a week of one another.

NATIONAL LIST VARIETAL EVALUATION

Grass and legume varieties in EU countries must be on a National List before they can be sold in that country or listed in the EU Common Catalogue, entry to which can be gained after two years on a member country’s National List. For National Listing the varieties must undergo comprehensive statutory assessment of varietal performance in VCU trials and genetic uniqueness in DUS trials. The latter trials, carried out by the Agri-Food and Biosciences Institute at Crossnacreevy in Northern Ireland on behalf of the UK, RoI and some other European countries, are necessary so that protective Plant Breeders’ Rights including royalties can be obtained for the breeder should the variety be successful commercially.

Spaced plants of candidate varieties undergoing tests for distinctness, uniformity andstability.

Photograph: Margaret Wallace

One of the characteristics determined in these tests is the date of ear emergence taken to be the average date when ears become visible on 50 per cent of the reproductive tillers in spaced plants. The date on which ears begin to develop in the young tillers in early spring (initiation) is determined by day length but the rate of development after initiation is dependent on temperature. So for a given variety the date of 50 per cent ear emergence (EE) can vary at a location from year to year by up to two to three weeks, depending upon early season temperatures. However, the relative differences of heading date between varieties remain fairly constant. As day length in March and early April is shorter at more northerly latitudes, heading date is progressively later; the decline in temperature with increasing altitude also delays heading due to a slower rate of development after heading is initiated.

The extent and methodology of performance testing varies from country to country within the EU. In the UK and RoI there are five centres each, in which varieties of the major species are sown in small plots: perennial, Italian and hybrid ryegrasses, timothy and white clover. Since 2005 the number of varieties entered has been between forty and forty-five, about 90 per cent of which have been perennial ryegrass. While about three-quarters of them pass DUS tests, the VCU test eliminates many and so only about a quarter of those varieties submitted enters the UK National List. Cocksfoot, meadow fescue, tall fescue, Westerwolds ryegrass and red clover varieties, together with some other species used occasionally in seed mixtures, are not officially evaluated in the UK or RoI as they are considered minor species. Government and plant breeders share the cost of assessment. The organizations responsible for continuity of National List varieties are known as ‘maintainers’, who may be UK agents of foreign firms.

Sowing grass plots in a grass variety evaluation trial.

In the current National List testing procedure in the UK, perennial ryegrass varieties are sown for two consecutive years. Each sowing is harvested for conservation in the first and third full harvest years (four to five cuts per annum, depending on growth rate, at 6cm cutting height) and simulated grazing in the second full harvest year (seven to nine cuts per annum at 3cm). Varieties are compared to long-standing standard or control varieties.

A harvester cutting grass plots to evaluate dry matter yield in a variety evaluation trial.

High level fertilization is used with adequate P2O5 and K2O application and a high annual rate of fertilizer N: 340kg/ha for the silage regime and 350kg/ha for the frequent cutting regime. In the RoI, each entered variety is also tested in two consecutive sowings but each lasts for two full harvest years. In each year a spring cut, two silage and three simulated grazing cuts in autumn are taken, reflecting the importance of dual- purpose swards in the country. In the UK, timothy varieties are also tested but only evaluated under a silage regime. Italian and hybrid ryegrasses are managed under a conservation regime when up to five cuts can be taken.