ALBERT

Notes: A sward of S24 perennial ryegrass was sampled at 4-weekly intervals over two seasons with either a Haldrup 1500 plot harvester or a hand-controlled mower fitted with a fixed reciprocating cutter bar. Plot dimensions were adjusted to the width of the machines'cutter bars (1.5 m and 1.0 m respectively) so that there were no discard areas to require removal. Plots were cut either once, or twice in opposite directions. After cutting, residual stubble heights and the proportion of ground surface covered by leaf laminae were recorded.Mean annual dry matter (DM) yields recorded in ten harvests made each year showed no overall significant difference between the machines. However, previous practice had been to sample plots with one pass of the hand-controlled mower and to trim the sampled area while removing the usual discard strips. The comparison of annual DM yields from one cut taken with the Haldrup or from two cuts taken with the mower, but with the yield at the second cut excluded, showed a mean advantage of 1.55 t DM ha−1 a−1 for the Haldrup technique or a 14.6% increase over previous practice.Cutting twice significantly (P〈0.001) reduced herbage production by a mean of 0.85 t DM ha−1 a−1, mean residual stubble height by 9.8 mm and the proportion of ground covered by leaf laminae by 9.8%. Provided that judgment is exercised when planning treatments and layout of trials, it is concluded that the Haldrup 1500 plot harvester is a valuable labour-saving tool. However, DM yields from trials cut frequently with this machine are likely to exceed those from similar trials cut with a hand-controlled mower, following the usual G.R.I. Staff (1961) technique.

Notes: Two experiments, each lasting approximately 12 months, were carried out at North Wyke, Devon, in 1982-83 (A) and 1983-84 (B), to investigate various sward managements following oversowing of white clover (Trifolium repens, cv. Grasslands Huia) at 4 kg ha-1 with a Hunter Rotary Strip-Seeder in June or July into the stubble of a permanent grass sward following conservation. Experimental managements comprised cutting, grazing with wether sheep or grass suppression by herbicide, as appropriate, in late summer/autumn (Phase I), winter (Phase II) and spring/early summer (Phase III).During Phase I, there was no differential effect on clover stolon development of lenient grazing at approximately 4-weekly intervals or topping at the same frequency to a similar height. Early in Phase II of Experiment A, grazed paddocks became so badly poached that no differences occurred between grazing either to early January or throughout the winter. Under drier conditions in Phase II of Experiment B, continuous grazing at either five (L) or ten (H) sheep ha-1 had no immediate effect on clover stolon development, but in a silage cut in June, paddocks formerly stocked at the lower rate yielded 40% more DM than those at the higher rate.Experiment A compared the use of a grass-suppressing herbicide, propyzamide, applied at 0.6 kg a.i. ha-1 in either October or February; in Experiment B it was applied in October. Prophyzamide applied at either time in Experiment A increased the clover content of herbage regrowing after the end of the experimental period from 16% to 36% (s.e.d. ± 3.9). In Experiment B, October application raised the clover contents of herbage cut in June 1984 from 10% (H) and 17% (L) to 32% (s.e.d.±5.9), and stolon lengths per m2 at the end of the summer period from 33 (H) and 56 (L) to 86m (s.e.d. ± 11.7). However, the effect of spraying propyzamide on subsequent herbage yields was erratic, and appeared to depend on the incidence of frost after application.In Phase III of Experiment A, continuous grazing was compared with a silage cut in June. At the end of the experiment there were 31 m m-2 of clover stolon in silaged areas compared with only 2.5 m m-2 following grazing (s.e.d.±6.6). Clover content and herbage yields were also significantly higher following conservation. In Experiment B in the same period, rotational grazing with a 14- or 35-day recovery interval was compared with a silage cut in June, with or without 100 kg N ha-1 applied in March. Application of N to the conservation treatment reduced clover stolon length per unit area, and in the regrowth in the post-experimental period the conservation treatment without N had the largest clover content (31% compared with 16-23% for other treatments, s.e.d. ± 3.6)

Notes: The effects of cutting frequency on dry matter yield, crop persistence and herbage quality of representative diploid and tetraploid varieties of broad red clover (Trifolium pratense) were investigated in two trials at Hurley in the period 1975–79.Pure-sown swards of broad red clover varieties were used in the first trial (A), while both pure-sown swards and those sown with a perennial ryegrass companion grass were included in the second trial (B).Tria1was cut three or six times per annum, trial B three, four or five times per annum. In both trials, the change from normal management of three cuts per annum to six (trial A) or five (trial B) cuts per annum reduced output, whether in terms of dry matter yield (trial A by 31%; trial B by 33%), N yield (trials A and B by 15%) or metabolizable energy (trial A by 24%; trial B by 28%), and in trial A also led to more rapid reduction in clover plant density. More frequent cutting also raised mean D–value (trial A by 5–3 units; trial B by 3–4 units) and N concentration (trial A by 64 g kg dry matter-1; trial B by 70 g kg dry matter-1). Tetraploid (4x) red clover varieties generally out–yielded diploid (2x) varieties, except in trial A in 1976 when, under drought conditions, Granta and Kuhn (both 2x) equalled the yield of Wensum (4x) and out–yielded Norseman and Maris Leda (both 4x).The companion grasses included in trial B formed a sequence from early to late flowering (Aberystwyth S24, Barlenna, Endura), and their inclusion raised dry matter yields and D-value, though it lowered N concentration in the mixed herbage. Highest annual dry matter yields in this trial, which received supplementary irrigation, were 1641 ha-1 from a pure–sown crop (Hungaropoly) and 205 t ha-1 from a mixture (Wensum/ Aberystwyth S24), from three cuts in the first harvest year. Aberystwyth S24 had the greatest effect in raising yields; though least effect on improving digestibility. Endura was the converse, and it was concluded that an intermediate-maturity variety such as Barlenna was the most satisfactory companion.Both trials A and B suggested that in south–east England, broad red clover can be considered only as a 2–year crop and that ways must be found to prolong its productive life. Strategies to increase the digestibility and hence the economic value of the crop by cutting more frequently than three times per year are unattractive because of the large fall in yield and relatively small improvement in digestibility and hence metabolizable energy concentration.