J. Øyen Særheim Research Station, N-4062 Klepp St., Norway
Introduction
Materials and methods
Results and discussion
References
The grassland farmer's need to reduce financial inputs and concern for the environment are two major constraints influencing grassland production and management practices in 1990s. These factors have resulted in increased interest in the use of white clover as a forage legume in many European countries (e.g. Frame et a1., 1992). The objective of these study was to develop guidelines for management of grass/white clover swards. Under Norwegian farming it is often desireable to integrate grassland used for grazing with land used for silage making. Simulation of grazing and silage cut systems was therefore included. Different methods of establishing grass/clover swards are reported elsewhere (Øyen, 1991).
Two seed mixtures with Trifolium repens L. were tested. One included the cultivar 'Mi1ka Pajbjerg" and the other 'Sandra'. In addition to 5 kg white clover seed per ha, both mixtures included Lolium perenne L. (15kg/ha). Phleum pratense L. (5 kg/ha) and Poa pratense L. (5 kg/ha). The two seed mixtures were subjected to three harvest regimes (G, S and GS), which were replicated in two blocks, viz;
G: Harvested every 4 week (simulated grazing) 20.5., 20.6., 16.7., 6.9.
GS: Spring grazing + silage cut 20.5., 20.6., 6.9.
S: Silage cut only 10.6., 16.7., 6.9.
On the G and GS treatments first harvest were taken at sward heights of 25 cm, and on the S treatment at early heading of perennial ryegrass.
A basic annual dressing of potassium (200 kg K/ha) and phosphorus (34 kg P/ha) were applied. In addition all plots received 40+ 40 kg N/ha in the spring and after 1st harvest respectively. Subsamples for dry matter (DM) determination were taken from each plot and these were also used for chemical analyses (NIRR) of the herbage. Botanical composition was determined by visual estimates at each harvest. Metabolisable energy (ME) was estimated by converting in vitro dry matter digestibility (IVDMD, %) according to the following formula, where ME is expressed in MJ per kg DM (ADAS, 1975):
ME = (0.98IVDMD-4.8)* 0.15
Net energy lactation and feed unit milk of the yield was calculated according to Van Es (1978) and Ekern (1991). The means were separated by use of Duncan's multiple range test.
The experiments were conducted at two sites, Særheim (58°46'N) and Karmøy (58°55'N) in south western Norway. Two trials were carried out at Særheim and one at Karmøy. Both experimental sites are close to the North Sea and have a typical maritime climate. Mean annual rainfall and temperature May-October is 470 mm and 12.8 °C respectively. The soils at both sites were a sandy loam type with pH of 6.2 and 6.4 at Karmøy and Særheim respectively.
No management x cultivar interactions were identified and therefore only main effects are listed in the tables. The silage system (S) produced a significantly higher DM-yield than either simulated grazing (G) or the grazing + silage (GS) treatments both at 1st and 2nd harvest, whereas the total DM-production were the same on the G and S systems (Table 1).
The frequent system (G) tended to increase the proportion of clover compared to late and infrequent silage cut, significant effect was only noticed in 2nd cut (Table 1). 'Sandra' competed better with perennial ryegrass than 'Milka' and had the highest clover content at all cuts, but the difference were most pronounced in 2nd + 3rd year (Figure 1). Good persistence, more erect growth habit and vigorous growth of 'Sandra' have also been reported from other trials (Frankow-Lindberg, 1991, Øyen et a1., 1991). The difference between cultivars is greater than reported earlier, and one reason for this may be the more frequent cutting and the use of perennial ryegrass as companion grass.
Table 1 Dry matter yield and content of clover (mean 2nd + 3rd production year 5 trials).
|
|
Dry matter, t/ha |
Clover, % |
||||||
|
Harvest No. |
Harvest No. |
|||||||
|
Harvest system Mixture |
1 |
2 |
3 |
4 |
Total |
1 |
2 |
3 |
|
G |
2.97b |
2.36b |
1.39b |
1.60 |
8.33a |
13a |
29a |
31a |
|
GS |
2.71b |
2.26b |
2.30a |
- |
7.27b |
12a |
25b |
27a |
|
S |
4.45a |
2.77a |
1.44b |
- |
8.66a |
11a |
19b |
25a |
|
Milka |
3.41a |
2.40a |
1.67a |
1.60a |
8.01a |
8b |
17b |
20b |
|
Sandra |
3.35a |
2.53a |
1.75a |
1.60a |
8.17a |
17a |
32a |
35a |
DM digestibility (DMD) was generally high for all harvests, especially the G and GS-treatments produced herbage with high DMD-values. The higher proportion of clover on the 'Sandra' mixture was also reflected in higher content of crude protein (Table 2).
Energy yield, expressed as feed units milk was greatest for the silage system (S) and least for the GS system (Table 3). In general, the trials demonstrated that high energy output per ha can be obtained by frequent harvesting of white clover/ryegrass swards under Norwegian conditions. The greater tolerance of white clover and perennial ryegrass to frequent cutting is also demonstrated by Basetti et a1. (1991).
Figure 1 Development of white clover during the season.
Table 2 In vitro dry matter digestibility (IVDMD) and crude protein at different harvest.
|
|
IVDMD, % |
Crude protein, % |
||||||
|
Harvest No. |
Harvest No. |
|||||||
|
Harvest system Mixture |
1 |
2 |
3 |
4 |
1 |
2 |
3 |
4 |
|
G |
84.3a |
77.6a |
75.8ab |
74.2 |
18.0a |
23.2a |
20.7a |
26.0 |
|
GS |
82.5ab |
77. 0a |
71.9b |
|
18.7a |
20.7a |
19.0a |
|
|
S |
79.7b |
76.4a |
79.4a |
|
15.6a |
16.5b |
24.4a |
|
|
Milka |
82.6a |
77. 1a |
75.3a |
74.1a |
16.0b |
18.7b |
20.1a |
25.3a |
|
Sandra |
81.7a |
76.9a |
76.2a |
74.3a |
18.8a |
21.5a |
22.6a |
26.8a |
Table 3 Energy yield as feed units milk per hectare. Mean of 5 trials.
|
Harvest system Mixture |
Harvest No. |
|
|||
|
1 |
2 |
3 |
4 |
Total |
|
|
G |
3080b |
2070b |
1520c |
1710 |
8370b |
|
GS |
2750c |
1970b |
2550a |
|
7270c |
|
S |
4570a |
2970a |
1860b |
|
9400a |
|
Milka |
3460a |
2280a |
1960a |
1710a |
8270a |
|
Sandra |
3470a |
2390a |
1990a |
1710a |
8430a |
ADAS (1975) Energy allowances and feeding systems for ruminants. HMSO, London 1975, pp. 70-71.
Basetti, P., Lüscher, A. and Nösberger, J. (1991) The influence of management on the floristic composition and sward density of a permanent meadow dominated by Lolium multiflorum. Wirtschafseigene Flitter. 37, 258-267.
Ekern, A. (1991) Nytt system for energivurdering av fôr til drøvtyggere. (A new system of energy evaluation of food for ruminants). Norsk landbruksforskning 5, 273-277.
Frame, J., Bax, J. and Bryden, G. (1992) Herbage quality of perennial ryegrass/white clover and N-fertilized ryegrass swards in intensively managed dairy systems. Proceedings of the 14th General Meeting of the European Grassland Federation. Lahti. Finland, pp. 180-184.
Frankow-Lindberg, B.E.(1991) Yield and persistence of large-leaved Scandinavian white clover cultivars grown for cutting in a nitrogen fertilized mixed swards and the effect of nitrogen fertilizer distribution. REUR. Technical Series. No. 19, 67-71. FAO. Rome 1991.
Van Es, A.J.H. (1978) Feed evaluation of ruminants. I. The system in use from May 1977 onwards in the Netherlands. Livestock Production Science. 5, 331-345.
Øyen, J., Rapp, K., Svenning, M.M. and Aasmo, M (1991) White clover: Review of recent research and development in Norway. HERBA. FAO Information Bulletin. No. 4, 28-31.
Øyen, J. (1991) Methods of establishing grass/clover swards. Norwegian Journal of Agricultural Sciences 5, 301-305.
