R.D. Sheldrick, R.H. Lavender and T.M. MartynInstitute of Grassland and Environmental Research North Wyke Research Station, Okehampton, Devon, UK.
Introduction
Materials and methods
Results
Conclusions
Acknowledgement
References
It has been suggested that the poor spring performance of grass-clover swards relative to N-fertilised grass may be due to a combination of the loss of white clover stolon and growing points over winter, and poor relative growth rates under subsequent cool growing conditions. To overcome this, selections for winter hardy, cold tolerant lines were successfully made at IGER, Aberystwyth from Swiss populations (Collins and Rhodes, 1991). One selection, cv. AberHerald showed DM yields in March over 250 per cent greater than a standard clover variety Menna (Rhodes and Fothergill, 1993). At Hurley, two selections (cvs. AberCrest and AberHerald) were tested in controlled environments in 1989, and their growth rates compared with white clover cv. Menna and perennial ryegrass cv. Melle (Davidson, 1990). There were no differences in growth rate between the three clovers under either a 12°C day/8°C night or 7°C day/3°C night regime, though they all grew less well than the ryegrass. At North Wyke, the same clover cultivars were sown in 1989 under field conditions in association with perennial ryegrass cv. Cropper and results 1990-92 are reported here.
The experiment was sown 15-16 June 1989 on an open field site at North Wyke Research Station. The soil at the site was a poorly drained silty clay loam. Before preparation of the seed-bed, the site had received 5t lime ha-1, and inputs of P and K to correct shortages of these nutrients. Perennial ryegrass cv. Cropper was drilled at 11.0 kg ha-1, then the clover broadcast at 2.7 kg ha-1, and ring rolled. The layout comprised four randomised blocks, with plots of the three grass-clover mixtures, each sub-divided into 4 sub-plots (1.5m x 5.0m), randomly numbered. Weather data were available from a meteorological station c. 400m away.
DM yields, and seasonal distribution of production.
Each year 1990-1992, sub-plots were cut with a Haldrup plot harvester from early March in weekly sequence, so that after the initial clearing cut, all sub-plots regrew for 28 days, following the technique of Corrall and Fenlon (1978). Graphs of the seasonal rates of DM production were constructed. All plots received P and K regularly, and the site was irrigated as necessary. Cutting continued on a weekly basis until the sub-plot sequence was completed in early November. Whenever the initial sub-plot in the sequence was harvested, an additional sub-sample of herbage was collected, and sorted into grass and clover fractions to determine clover DM yield and the percentage clover contribution.
Clover morphology
In November 1990, March 1991, November 1991 and March 1992, twelve 10cm diameter turf discs were taken to the laboratory from each plot (three per sub-plot) and the total length of clover stolon, its dry weight, and the number of active growing points recorded, in order to determine the comparative losses of stolon material and growing points over the 1990-91 and 1991-92 winters.
Seasonal production
Fig. 1 shows the seasonal changes in the rate of DM production in kg ha-1 day-1. At times during 1990 and 1991, Menna plots showed superior DM production rates to at least one, and at times both of the selected clovers. However, there were no statistically significant differences in early season growth.
Table 1. Annual DM yields of mixed herbage, and of clover DM (t ha-1) in 8 cuts per annum.
|
Clover cv. |
1990 |
1991 |
1992 |
|||
|
Annual DM Yld |
Clover DM Yld |
Annual DM Yld |
Clover DM Yld |
Annual DM Yld |
Clover DM Yld |
|
|
AberCrest |
9.0 |
5.0 |
10.3 |
6.9 |
9.1 |
5.6 |
|
AberHerald |
10.1 |
6.2 |
10.0 |
7.2 |
8.2 |
4.9 |
|
Menna |
9.9 |
6.1 |
10.9 |
7.6 |
8.8 |
5.1 |
|
Significance |
NS |
NS |
NS |
P>0.05 |
NS |
NS |
|
s.e.d. |
0.42 |
0.44 |
0.36 |
0.16 |
0.43 |
0.54 |
Annual yields
Total herbage DM yields and yields of clover DM are shown in Table 1. The data generally show no statistically significant differences, except for the yield of clover DM in 1991, where the yield from Menna exceeds that from either AberCrest or AberHerald.
Clover morphology - changes over winter
Both winters 1990-1991 and 1991-1992 were generally mild. During a cold two week period in February 1991, there was a light snow cover. Though AberHerald had greater weights of stolon per m2, no significant differences were found between clover varieties in the ratio of their post-winter (March) stolon measurements to the pre-winter values, in either winter.
1. No significant differences were found in early season rates of DM production from swards of Cropper perennial ryegrass, with AberCrest, AberHerald or Menna white clover.
2. No significant differences were found in total annual DM yields of herbage from the three cultivars.
3. No significant differences were found between clover varieties in the ratio of post to pre-winter values for stolon length, weight or the number of active growing points.
This research formed part of a commission from the Ministry of Agriculture Fisheries and Food, London.
COLLINS, R.P. and RHODES, I. (1991) Genetic variation in cold tolerance and spring growth in white clover. In: White Clover Development in Europe. Meeting of FAO Sub-Network on Lowland Pastures and Fodder Crops, Polcenigo, Italy, Oct 1990, REUR Technical Series 19, 11-14.
DAVIDSON, I. (1990) Low temperature growth in ecotypes of white clover. In: Robson, M. (Ed.) Institute for Grassland and Animal Production Report 1989, p. 16.
CORRALL, A.J. and FENLON, J.S. (1978) A comparative method for describing the seasonal distribution of production from grasses. Journal of Agricultural Science, Cambridge. 91, 61-67.
RHODES, I. and FOTHERGILL, M. (1993) White clover breeding In: AFRC Institute of Grassland and Environmental Research. 1992 Report, pp. 33-34.
Fig. 1 Seasonal changes in rate of DM production (kg ha-1 day-1)
