Anjo Elgersma and Hans Schlepers
Wageningen Agricultural University, Department of Agronomy, Haarweg 333, 6709 RZ Wageningen, The Netherlands
Materials and methods
Results and discussion
Combinations of two varieties of perennial ryegrass with contrasting growth habits and three white clovers with different leaf sizes have been evaluated in The Netherlands under two cutting regimes since 1991 to study white clover persistence. Initial results were presented by Elgersma et al. (1993). This paper presents further results up until spring 1995.
The cutting trial was established in April 1991 on heavy river clay at Wageningen, The Netherlands. The perennial ryegrass varieties Condesa (tetraploid) and Barlet (diploid, erect) each were sown alone or mixed with the white clover varieties Alice (large-leaved), Retor (medium-leaved) and Gwenda (small-leaved). Thus, there were six mixtures and two grass monocultures. The experimental design was three replicates of a split-plot, randomized-block layout with cutting frequency as main factor and mixture as subfactor. Each year the soil was fertilized with P and K as required, but no N was applied. Starting in 1992, all entries were cut at approximately either 1200 or 2000 kg DM ha-1 (treatments designated as F1200 and F2000, respectively) with a Haldrup forage harvester at 5 cm sward height. At each harvest DM yield of grass, clover leaves and clover flowers (if present) were calculated per plot (for more experimental details, see Elgersma et al., 1993). Analyses of variance were carried out on total, grass and clover DM yields. The dried materials were bulked per grass/clover combination, and for grass and clover separately, and ground to determine the N concentration and the in vitro digestibility of organic matter (IVDOM).
Performance and management
The summer of 1992 was very warm. The F1200 treatment was cut 9 times and F2000 7 times. The grass monocultures performed very poorly due to shortage of N and to drought, but the mixtures were much less affected by drought. The winter 1992/93 was rather mild; spring and early summer of 1993 were warm and late summer, autumn and winter were very wet. There was a sudden heavy frost in February 1994. Spring 1994 was very wet, and the first two cuts were taken at higher DM yields than was intended. The summer of 1994 was very hot and dry and the trial was irrigated twice. In 1993 and 1994 the F1200 was cut 8 and 7 times, and F2000 6 and 5 times, respectively. Because the grass monocultures hardly yielded much, they were only cut a few times during these years and will not be considered in this paper.
Figure 1. The annual harvested DM yield of perennial ryegrass (Lp) - white clover (Tr) mixtures at two cutting frequencies during 1992-1994.
Grass and clover yield
The mixtures with clover cv. Alice yielded most during the whole season in all three harvest years and at both cutting frequencies (Figure 1). There was a highly significant (P < 0.001) effect of mixture on DM yield, which was caused by the clover variety. There was no effect of grass variety. The F2000 threatment consistently yielded more than F1200 for all mixtures throughout the years.
Fluctuations in the clover content are shown in Figure 2 (F2000 only). The clover content dropped sharply in all mixtures in February 1994 after a sudden heavy frost following a mild winter, but recovered during the growing season. Throughout the years in both cutting frequencies, the mixtures with cv. Alice always had the highest clover content, and the mixtures with cv. Retor tended to have less clover than those with cv. Gwenda.
Figure 2. The percentage white clover (DM basis) in the harvested material of six grass/clover mixtures cut at approximately 2000 kg DM ha-1.
Date (days from January 1)
Figure 3. The IVDOM (%) in the harvested white clover and perennial ryegrass herbage in 1992 and 1994
Nitrogen concentration and digestibility
The N concentration was always slightly higher in F1200 than in F2000. The N concentration of clover DM ranged from 4-5.5% and there were no differences between clover varieties; in grass N ranged from 1.5 - 4%. The grass in mixtures with Alice generally had a higher N concentration than grass grown with other clover varieties. The IVDOM was higher in clover than in grass, except for one harvest date in July 1992 (Figure 3) which coincided with clover flowering.
There was not much difference between the three clover varieties. Similarly, both grass varieties had similar IVDOM. In 1994 the IVDOM of clover (Alice) was similar to the level in 1992, but the IVDOM of grass (Barlet) was much lower during June - September 1994 than in 1992 (not shown).
The IVDOM of the mixtures was higher in 1992 than in 1994, owing to the low IVDOM of the grass component in 1994. There were no differences among varieties. The IVDOM in the F1200 treatment was higher than that in F2000, especially in 1994.
Companion grass variety did not affect the clover content or yield in the mixtures, but the effect of clover variety was very pronounced. The mixtures with the large-leaved variety Alice produced the highest total yield, the highest clover yield and (in 1992 and 1993) the lowest grass yield, and generally had the highest N concentration in the harvested herbage. The clover content remained high throughout years and recovered fully from frost damage during the growing season of 1994. The IVDOM was generally higher in clover than in grass. No differences in IVDOM were found among clover or grass varieties.
ELGERSMA, A., SCHLEPERS, H. and WENUM, J.H. VAN (1993). Performance of white clover - perennial ryegrass mixtures under cutting. White clover in Europe: State of the Art. REUR Technical Series. 29, 95-97.