Department of Grass and Forage Science, Christian-Albrechts-University, 24098 Kiel, Germany
SUMMARY
In a field experiment the yield formation of four white clover cultivars grown in binary mixtures with two perennial ryegrass cultivars was investigated in 1995 and 1996. Every week during the vegetation period, the yield of a four-week-old clover/grass sward was determined, and from this a seasonal production curve was calculated. In addition, the different clover fractions, leaf area index and selected quality parameters were measured. The yield formation of white clover was strongly influenced by the weather in both years. The coolness and extreme drought in the spring of 1996 impaired the leaf development and the highest daily growth rates of 4 g m-2 were 3 g below the growth rates of the preceding year. There were significant differences in clover growth between cv. Huia and the other cultivars. The low overwintering rate of cv. Huia resulted in a very low growth performance in spring 1996, and therefore in a poor ability to compete with the grass. There were only slight differences between the years and the cultivars concerning the nutritive value of white clover. During flowering, digestibility decreased with raising bud development.
The impact of climatic factors on the yield performance of clover/grass swards was determined by an evaluation of the data from the year 1995 using a dynamic model.
Keywords: nutritive value, Trifolium repens L. white clover, yield formation
INTRODUCTION
The dynamics of white clover growth during the vegetation period is influenced by many factors. White clover tends to show great fluctuations in yield and it is difficult to achieve and maintain a target proportion in a clover/grass sward. In this study, the yielding ability and nutritive value of different white clover cultivars combined with perennial ryegrass were investigated.
MATERIALS AND METHODS
The experiment was established near Kiel in May 1994. The experimental site was located in the east of Schleswig-Holstein in a hilly landscape with sandy loamy Cambisol (pH: 6.7), average yearly precipitation of 716 mm and an average yearly temperature of 7.8°C.
The design of the experiment was a randomized block with three replicates.
The trial consisted of four white clover cvs., AberHerald, Huia, Milkanova and N.F.G. Gigant. These were sown in a mixture with two perennial ryegrass cvs., Preference (medium-late-heading) and Vigor (late-heading), at seeding rates of 2 kg ha-1 clover seed and 23 kg ha-1 grass seed. The plots received 30 kg ha-1 N at the beginning of the vegetation period.
Figure 1. Effect of clover cultivar on the development of the daily growth rates (GR; g DM m-2 day-1) of white clover during the vegetation period 1995 and 1996 (mean of two grass cvs).
Figure 2. Effect of clover cultivar on the development of a) Digestibility (°/a OM); and b) Crude protein content (% DM) of white clover during the vegetation period 1995 (mean of two grass cvs).
RESULTS AND DISCUSSION
The yield formation of the clover/grass sward was in both years mainly determined by weather conditions. The cool spring in 1996 with concomitant extreme drought affected white clover growth. The average leaf area was greatly reduced and the highest daily growth rates of 4 g m-2 day-1 were 3 g below the growth rates of the preceding year (Figure 1). In 1996, an average of 40 percent white clover was observed, compared with approximately 73 percent in 1995. The comparisons of the clover cultivars showed only clear differences between Huia and the other cultivars. The low overwintering of these cultivar results in a very low growth performance and therefore in a poor ability to compete with the grass in spring.
There were only slight differences between years and cultivars with respect to the qualitative development of the white clover. During flowering, the nutritive value decreased and digestibility reached its lowest level during the peak of flowering at the end of July (Figure 2). Differences in bud development influenced the digestibility of the cultivars. Due to their strong flowering Gigant and Milkanova had the lowest digestibility in summer. Strikingly Aberherald showed a low digestibility and crude protein content in spring and autumn 1995. It remains to be seen if this is a consistent characteristic of this cultivar.
The relationship between climatic factors and yield performance can be investigated by using the data from 1995 in the dynamic model FOSIM of Kornher and Nyman (1992). The modelling approach was parameterized on the set of data from the year 1995 (r2 = 88%). The data set of this year allows to stimulate the yield of a cloverglass sward for different weather conditions snd different utilisation strategies.
REFERENCES
Kornher A. and Nyman P. 1992. A model for prediction of growth and quality charge of grass swards. In Proc. of the 14th General Meeting of the Grassland Federation, Lahti, 378-382.
