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Evaluation of white clover under grazing management

An Ghesquiere and Dirk Reheul

Rijksstation voor Plantenveredeling, Merelbeke, Belgium

Introduction
Materials and methods
Results and discussion
Conclusions

Introduction

White clover is pre-eminently used for grazing. Therefore, it is important to evaluate white clover under grazing conditions in the breeding programme. The aim of this study was to test white clover varieties, populations and clones under a grazing management.

Materials and methods

In September 1992 we laid out a grazing trial in 3 replicates with plots of 20 m2. A 1:1.5 mixture (based on the number of germinating seeds) of Meltra, a tetraploid and Melvina, a diploid perennial ryegrass was drilled at a rate of 40 kg ha-1. Immediately after the drilling of the grass, the following varieties and populations of white clover were broadcasted at 3.5 kg ha-1:

19 varieties:

- 4 large leaved: Crau; Major; Lune de Mai; Regal
- 4 medium-large leaved: Alice; Siwan; Olwen; Sabeda
- 7 medium leaved: Merwi; Milkanova; Sonja; Donna; Nesta; Lirepa; Milka
- 2 small leaved: Barbian; SI 84
- Lustar and El Lucero, two varieties of unknown leafsize

10 breeding populations (selected under cutting management): 2643A; 3012A; 3020A; 3032A; 3034A; 3077A; 3079A; 3122A; 3123A; 3124A

The clover seeds were pressed into the soil by a Cambridge roller.

Additionally we have planted 15 clones of white clover (mostly ecotypes): there were 9 individuals of the same genotype per plot.

In the spring of 1993 a dressing of 75 N ha-1 was applied and in the summer 50 N ha-1. In 1994 the trial only received a dressing of 50 N ha-1 in the spring.

The trial was intensively grazed by sheep during the growing season (in 1993 from the end of April to mid-November and in 1994 from the beginning of May to the beginning of December). The stocking rate was adapted to the grass growth and the sward was kept at a surface height of approximately 4-6 cm. During these two growing seasons the plots were scored on the presence of white clover (visual score from 1 to 7:1 = almost no white clover). The percentage white clover that is represented by this score varied depending on the time of scoring, since we are for breeding purposes interested in relative and not in absolute values.

Results and discussion

In October 1992 the emergence of the white clover was scored. Due to a very erratic emergence the varieties Crau, Sabeda, Merwi and Lustar and the breeding population 303 2A were excluded from further results. White clover was evaluated 5 times during the growing season of 1993 and 4 times during the growing season of 1994. None of the clones performed well and they all disappeared under grazing.

Figure 1. Mean score for the presence of white clover under sheep grazing management with varieties grouped according to the leafsize (1 = almost no white clover; 7 = much white clover)

Table 1 and 2 give the results of 15 varieties and 9 populations of white clover, respectively. Large leaved varieties as Major, Lune de Mai and Regal nearly disappeared under this grazing management. The medium-large leaved varieties Siwan and Olwen were not persistent, although Alice, also a medium-large leaved variety performed well. Most of the medium-leaved varieties persisted well. The performance of the two small leaved varieties Barbian and S184 was by far the best. Most of the breeding populations were not very persistent.

Figure 1 shows the mean scores for white clover cover during the two growing seasons and shows clearly that the larger the leaf size, the less persistent the white clover was under this sheep grazing management.

Conclusions

After two years of an intensive grazing management with sheep, only 9 of the 29 varieties and populations performed well enough to be used for further breeding purposes.

Table 1. Mean visual scores for the presence of 15 white clover varieties in a grass/white clover sward during two years under a grazing management (1 = almost no white clover; 7 = much clover)

Variety

1992

1993

1994

19.10

26.03

20.04

17.06

19.07

29.10

30.03

20.07

06.09

26.10

Major

2.7

1.7

2.7

1.7

2.3

2.3

2.3

2.0

2.0

1.3

Lune de Mai

3.7

3.7

3.7

4.7

4.0

3.3

3.7

2.0

3.3

1.7

Regal

5.3

5.3

5.0

2.7

3.3

2.7

2.0

2.0

1.3

1.7

Alice

3.7

3.3

3.7

4.0

4.7

5.0

5.0

4.7

4.7

3.8

Siwan

2.3

1.3

3.7

2.0

3.0

2.7

3.3

2.7

4.0

2.2

Olwen

3.0

3.3

3.3

2.3

2.7

2.0

2.3

1.7

3.0

2.0

Milkanova

4.3

3.7

5.0

4.7

5.0

4.3

5.0

3.0

5.0

3.0

Sonja

4.7

4.3

5.0

4.7

6.0

5.0

5.0

5.3

5.7

4.0

Donna

2.3

1.0

2.7

2.3

3.7

3.7

4.3

4.0

4.7

3.0

Nesta

2.3

3.0

3.0

3.7

3.7

4.3

4.7

4.3

5.3

3.8

Lirepa

5.0

3.7

4.7

4.3

5.7

5.3

5.0

4.7

5.7

4.2

Milka

3.7

1.3

2.7

4.0

4.7

4.3

4.3

4.7

5.0

3.7

Barbian

3.3

2.3

4.0

5.7

6.0

5.7

6.0

5.7

7.0

6.0

S184

4.0

3.7

4.3

5.3

6.0

6.0

6.0

6.0

7.0

6.0

El Lucero

4.0

3.7

5.0

4.0

4.3

4.3

4.0

2.3

4.3

2.7

Table 2. Mean visual scores for the presence of 9 populations of white clover in a grass/white clover sward during two years under a grazing management (1 = almost no white clover; 7 = much clover)

Population

1992

1993

1994

19.10

26.03

20.04

17.06

19.07

29.10

30.03

20.07

06.09

26.10

2643 A

5.0

3.7

5.7

4.0

5.0

4.0

4.3

2.0

5.0

3.0

3012 A

4.3

3.3

4.7

4.0

5.3

3.3

4.7

4.0

4.3

2.2

3020 A

5.0

4.0

4.7

3.7

4.7

3.0

3.0

3.7

4.7

2.3

3034 A

3.0

1.3

3.0

2.7

3.7

2.7

3.0

3.0

4.0

2.8

3077 A

5.3

4.3

5.3

4.0

5.0

4.3

5.0

3.7

5.3

3.2

3079 A

4.7

4.0

5.3

5.0

5.0

4.3

4.7

4.0

4.7

3.0

3122 A

4.7

4.7

5.0

2.7

4.0

3.0

3.3

2.3

4.0

2.0

3123 A

4.3

4.3

5.3

4.0

5.3

4.7

4.3

3.3

5.3

3.7

3124 A

4.3

4.3

4.7

3.7

4.7

3.0

4.3

2.7

4.7

1.8


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