Marianna Warda
Department of Grassland, Agricultural University Akademicka 15, 20-950 Lublin 1, Poland
Introduction
Materials and methods
Results and discussion
Conclusion
References
Content of white clover in pastures is a function of competitive effects of the associated grasses (Ennik, 1970, Harris, 1987, Haynes, 1980), habitat factors (Chestnutt and Lowe, 1970, Warda, 1987) and management (Frame and Newbould, 1986, Gibson and Cope, 1985). It is difficult to determine the dominant influence of any one from the above mentioned factors because of their interaction.
Two experiments investigated the possibility that soil types, together with their fertility and acidity might affect productivity and persistency of white clover varieties in the mixed sward.
The studies were carried out on cattle grazed pastures during the years 1988-1991. Experiment A was established on black soil, developed from loose sand. The soil was of moderate availability in phosphorus, potassium and microelements and very low in magnesium, with a pH of 4.0. Experiment B was located on brown soil, developed from loess. This soil was high in phosphorus and magnesium, but low in potassium, with a pH of 6.9.
Two medium-leaved varieties of white clover (Anda, Santa) and a large-leaved one (Radzikowska) were sown in two-species (A) and four-species mixtures (B) with perennial ryegrass, meadow fescue and cocksfoot. The pasture fertilization included 90 kg ha-1 N (in three equal dressings each season,-following the first, second and third grazing), 70 kg ha-1 P2O5 and 120 kg ha-1 K2O annually. During the grazing season pastures were grazed four to five times by cattle. DM yields and botanical analyses were assessed on all plots before the first and fourth grazing each year.
Average DM yields in the both experiments were similar (Figure 1). Type of soil did not significantly affect pasture productivity. Important differences in the yields of the mixed swards were caused by white clover variety. The productivity of the sward containing the large-leaved variety of white clover, Radzikowska, was highest on both soils.
Figure 2. Content of white clover (% by weight) in the mixed sward
However, soil conditions influenced persistency of white clover (Figure 2). Clover did not persist well under very acid black soil conditions even in the pasture fertilized only with 90 kg ha-1 N, but growing in the treatment without N fertilization, it persisted much better (Warda, 1995). After four years of pasture utilization, the content of white clover in the sward ranged between 0,1 and 7,5%. The last value was characteristic of the Santa variety. Content of white clover in the pasture sward established on the brown neutral soil was significantly higher and in the last year of the study ranged from 9.4 to 17%. Varieties may be classified in the following order of decreasing persistency: Radzikowska > Anda > Santa.
Nutritional soil factors (pH, available plant nutrients) affect the persistency of white clover in the pasture sward, but their influence on the productivity of grass/clover sward in low-input pastures seems to be insignificant.
CHESTNUTT, D.M.B. and LOWE, J. (1970).(J.Lowe, ed.). Agronomy of white clover In: White Clover Research. Occasional Symposium of the British Grassland Society, No. 6, pp. 191-213.
ENNIK, G.C. (1970).(J. Lowe, ed.). White clover/grass relationships: competition effects in field and laboratory. In: White Clover Research, Occasional Symposium of the British Grassland Society, No. 6, pp. 165-174.
FRAME, J. and NEWBOULD, P. (1986). Agronomy of white clover. Advances in Agronomy, 40, 1-88.
GIBSON, P.B. and COPE, W.A. (1985). White clover. In: Clover Science and Technology (N.L. Taylor, ed.), pp. 471-490.
HARRIS, W. (1987). Population dynamics and competition. In: White Clover (M.J. Baker and M.W. Williams, eds), pp. 203-297).
HAYNES, R.J. (1980). Competitive aspects of the grass-legume association. Advances in Agronomy. 33, 227-261.
WARDA, M. (1987). The influence of mixture components and habitat conditions on the maintenance of certain species of low grasses and white clover in the sward of pastures for sheep. (In Polish). Annales Univ. Mariae Curie-Sklodowska. sectio E, XLII, 129-135.
WARDA, M.(1995). Seasonal changes in species composition of clover/grass sward under pasture utilization conditions (In Polish). Annales Univ. Mariae Curie-Sklodowska. sectio E, L - Supplementum, 113-116.
