Dr Piotr Stypiñski Department of Grassland The Warsaw Agricultural University 02-528 Warsaw, Rakowiscka 26/30 POLAND
Introduction
Material and methods
Results and discussion
Conclusions
References
In recent years great interest in white clover has been observed in Europe (Laidlaw and Frame, 1988). One reason for this is that the grass/clover mixtures have a high nutritional value and allow quality milk and meat production from grassland (Thomson, 1981). White clover, in comparison with grasses, contains more protein and macro and micro nutrients. It is also characterised by high digestibility and palatability. It has been proved in many experiments that nitrogen fixation by white clover is between 120-250 kg N/ha/year (Frame and Newbould, 1986). However, the question is whether this nitrogen can be used by companion grasses. One of the main goals of five years field trials at the Experimental Station of the Agricultural University in Warsaw was to estimate the influence of white clover on grass chemical composition in pasture mixtures.
The experiments were carried out in the years 1987-90 on the pastures located on black loam soil. In 1986 the mixture of white clover with three grass species - cocksfoot, ryegrass and timothy - was sown in four replications. The same grasses and white clover were also examined in the pure stand. The following fertilisation was applied each year: 120 kg N, 60 kg P2O5 and 120 kg K2O. A rotational grazing system was used in the experiment (four rotations per year). In each rotation, yields, botanical and chemical composition were determined. Chemical analysis (ash, crude protein, pure protein, crude fibre, P, K, Ca, Mg, Na) were done by the use of the standard methods separately for grasses and clover. Digestibility and metabolic energy concentration in clover, grasses and mixtures were also calculated.
The examinations confirmed that the grass/clover mixtures have better chemical composition and higher nutritional value in comparison with pure grasses (Table 1). The chemical analysis also demonstrated the positive influence of white clover on its companion grasses. The grasses growing with clover contained on average 2.3% crude protein and 1.2% pure protein more than the same grasses growing without clover (Table 2).
Table 1. The comparison of chemical composition of white clover, grasses and grass/clover mixtures. Means from the years 1987-1991
|
|
Crude protein |
Pure Protein |
Crude fibre |
Ash |
DOM |
Energy |
P |
K |
Ca |
Mg |
Na |
|
%DM |
%DM |
%DM |
%DM |
|
MJ/kg |
in % of DM |
|||||
|
White clover |
26.6 |
19.6 |
19.9 |
8.5 |
75.5 |
10.38 |
0.49 |
2.6 |
0.9 |
0.2 |
0.30 |
|
Grasses |
16.1 |
10.6 |
28.2 |
7.4 |
62.9 |
8.52 |
0.46 |
3.1 |
0.4 |
0.1 |
0.21 |
|
Mixture |
21.4 |
13.6 |
25.7 |
7.7 |
67.4 |
9.19 |
0.46 |
2.7 |
0.6 |
0.2 |
0.26 |
Table 2. The influence of white clover on crude protein and crude fibre content in companion grasses in grass/clover mixtures
|
|
Year |
Crude protein |
Pure protein |
Crude fibre |
|
% of DM |
% of DM |
% of DM |
||
|
Grasses growing without clover |
1987 |
13.7 |
9.2 |
23.8 |
|
1988 |
16.3 |
10.9 |
23.8 |
|
|
1989 |
14.3 |
8.3 |
23.3 |
|
|
1990 |
13.8 |
8.8 |
23.8 |
|
|
1991 |
13.3 |
9.3 |
30.3 |
|
|
Mean |
|
14.3 |
9.3 |
26.0 |
|
Grasses growing without clover |
1987 |
13.9 |
9.3 |
23.9 |
|
1988 |
18.4 |
12.1 |
21.9 |
|
|
1989 |
16.8 |
8.7 |
23.6 |
|
|
1990 |
16.9 |
10.4 |
25.3 |
|
|
1991 |
16.9 |
11.0 |
25.9 |
|
|
Mean |
|
16.6 |
10.5 |
24.1 |
The protein effect did not occur in the first year but strongly appeared in the third and subsequent years in spite of the fact that the percentage of white clover in the sward was rather low in these years. This can be explained by the decomposition of clover root systems and mineralisation of nitrogen fixed by Rhizobium trifolii. The released nitrogen is then used by companion grasses. The direct transfer of N from clover to grass is impossible, as was previously reported by Ennik (1981) and Paris and Ta (1985). It has not been found that white clover had any influence on the macro-nutrients content in companion grasses.
1. White clover improved the pasture value and grass/clover mixtures are better than pure grasses (higher digestibility, energy concentration, protein and macro-nutrients content).
2. The protein content was higher in the grasses which were grown together with clover compared to grasses grown alone.
3. The positive effect of white clover on quality of companion grasses is observed after some years after sowing, even if the percentage of clover is falling.
ENNIK, G.C. (1981). Grass/clover competition especially in relation to N fertilisation. Occ. Symp. No. 13, BGS Plant Physiology and Herbage Production (ed. C.E. Wright), 169-172.
PARIS, M.A. and TA, T.O. (1985). Study of nitrogen transfer from alfalfa to associated timothy under field conditions. Proc. of XV Int. Grassland Congress, Kyoto, 448-449.
FRAME, J. and NEWBOULD, P. (1988). Agronomy of white clover, advances in agronomy, 41, 1-88.
LAIDLAW, A.S. and FRAME, J. (1988). Maximising the use of legume in grassland systems. Proc. of XII General Meeting of EOF, Dublin, 34-46.
THOMSON, D.J. (1981). Feed quality and utilisation of grass/white clover swards. Proc. of 5th Study Conference of SAC "Legumes in Grassland", 25-35.
