over a period of 6 years without any application of fertilizer N. The practical agricultural implications of using red clover are discussed. AbstractThree diploid-Sabtoron, Violetta and Essexand three tetraploid-Hungaropoly, Teroba and Red Head-red clover cultivars were sown alone and with each of three companion grassestimothy (S48), tall fescue {S170) and perennial ryegrass (S24). The productivity and persistence of the red clover cultivars were compared. Results obtained over the first four harvest years were presented in an earlier paper (McBratney, 1981) and this paper presents results from the fifth and sixth (final) harvest years.The low yield obtained in the fifth and sixth year from Essex under each seeding treatment indicated a deterioration in its persistency or vigour or hoth. In the fifth year the remaining two diploids, Sabtoron and Violetta, were as highly productive and persistent as the three tetraploids but in the sixth year the decrease in productivity was greater in the diploids than in the tetraploids. In the fifth year Teroba, the highest yielder, produced 9-8 t total DM ha"' over all seeding treatments of which 73% was clover DM; in the sixth year Teroba was again highest yielding, producing 9-3 t ha"' with 67% clover content. Tall fescue was the most consistent companion grass in the mixed swards, in the sixth year contributing 53% grass DM to the total 8 8 t DM harvested ha"'.The trial demonstrates the potential of a number of red clover cultivars grown either pure or with a suitable perennial grass to achieve and maintain a high output of herbage of good quality Correspondence: Miss I. M. McBrainey, DcpartmenI of Agriculture for Norlhem Ireland, Agricultural Botany Research Division. Newforge l^ne, Belfast UK, BT9 5PX. lntrnductioDIn a previous publication (McBratney, 1981) the author reviewed the literature, outlined the objectives, described the materials and methods and presented the results obtained over the first four harvest years (1974)(1975)(1976)(1977) of an experiment comparing yield, quality and persistency of six cultivars of red clover (Trifotium praten.

Six red clover cultivars, three diploid-Essex, Sabtoron and Violetta-and three tetraploidTeroba, Red Head and Hungaropoly-were sown alone and with each of three companion grasses-timothy (S48), tall fescue (SI70) and perennial ryegrass (S24). The productivity and persistency of the red clover cultivars were compared over 4 years. Dry matter (DM) yield, DM digestibility and the crude protein (CP) concentration were assessed and botanical analyses conducted on herbage samples from each treatment at each of three harvests per annum. Annual fertilizer application consisted of 165 kg P and 312 kg K ha-'.Comparing clover cultivars alone Essex was significantly less productive and less persistent than the other five cultivars. Yield and persistency ofthe five other cultivars did not differ markedly within years with the exception that the diploids were significantly less productive than the tetraploids in the fourth year. Over all 4 years mean annual total DM and clover DM yields ofthe five cultivars were between 12-4 and 13-2 t ha"' and between 9-8 (79 7% of total DM yield) and 10-6 (83-5%) t ha"' respectively, and differences were not significant.Up to the end of the third year there was little or no advantage gained by the inclusion of a companion grass, annual total DM yields being between 11 4 and 14-71 ha"' for clover alone and between 100 and 14-7 t ha"' for clover-grass mixtures. In the fourth year there was an overall tendency for the yield of the clover alone to be lower, between 7-6 and 121 t ha "', than that of the clover-grass mixture, between 8-8 and 13-1 t ha"', and this was more pronounced with the diploid than with the tetraploid clover cultivars. Sown with companion grasses, Essex and Hungaropoly were lower in yield and in contribution than the other cultivars over the 4 years. The influence of the companion grass on total dry matter yield showed that the contribution of timothy was low relative to that made by tall fescue and perennial ryegrass. Perennial ryegrass made the most varied contribution from year to year. Tall fescue was the most consistent contributor with all clover cultivars and at the end of 4 years both yield and clover-grass balance had not changed materially.No pronounced differences in DM digestibility were evident between treatments.Crude protein concentration ofthe pure clover was similar to that of the clover-timothy treatments and both would appear to be superior to either the clover-perennial ryegrass or clover-tali fescue mixtures.It is considered that red clover dominant swards are suitable for use under a cutting regime and can provide high yields of DM at a low cost for up to 4 years. Such swards are self-sufficient in N and in addition soil N accumulation can be exploited in the production of succeeding crops.

between the first and second cut might be reduced, and it is concluded that more benefit is derived from red clover when medium or late heading ryegrasses are used as companion grasses. AbstractReplicated plots of Hungaropoly red clover were sown on a sterilized area in May 1975 alone (seed rate 11 kg ha~') or with one of six cultivars of perennial ryegrass (seed rate 3 5 kg ha~') viz. Cropper and S24 (early heading), Barlenna and Hora (medium heading) and Melle and Perma (late heading). In 1976 and 1977 primary growth was cut at one of four dates ranging from midMay to mid-June and thereafter plots were harvested twice each year.Varying the time of first cut did not have a significant effect on total dry matter (DM) yield in either year despite differences in means of cutting treatments on annual red clover yields of the order of 6-9%.In some companion grass treatments total DM yield in 1976 was increased and total red clover yield and percentage red clover contribution were reduced relative to swards sown only with red clover. In 1977 a similar but non-significant trend was found. Swards containing early ryegrasses had higher total herbage DM yields but lower red clover yields and contents than all other swards at the first harvest in both years.Delay in date of taking the first harvest in 1976 reduced DM digestibility in the first cut and increased it in the second in both years.It is suggested that by cutting early and increasing the number of harvests from three to four per year, differences in the content of red clover Correspondence; Dr A. S.

may be restored by the application of N fertilizer, particularly where the clover was seeded with a highly productive companion grass. AbstractThree diploid red clover cultivars-Sabtoron, Violetta and Essex-and three tetraploids, Hungaropoly, Teroba and Red Head, were sown separately in pure culture and with each of three companion grasses: timothy (Aberystwyth S48), tall fescue (Aberystwyth SI70) and perennial ryegrass (Aberystwyth S24).The eifects of fertilizer N on yield and on clover/grass ratio over a 2-year period (seventh and eighth harvest years) subsequent to 6 harvest years during which no N fertilizer was applied were investigated. The data for productivity and persistence have already been published (McBratney, 1981;1984).Application of fertilizer N increased DM yields in the eighth year. In this year, the highest yield, 11 -91 ha~', averaged over the six clover cultivars, was given in association with tall fescue. Tall fescue contributed 90% of this yield. Clover content continued to decrease in all swards but the decrease was greatest in the swards receiving fertilizer N. The yield of clover DM averaged over the six cultivars under N treatment declined from 5-61 ha"' in the seventh year to only 0 41 ha"' in the eighth year.The results from this trial demonstrate the potential of red clover sown either pure or in mixture with a suitable perennial grass, to maintain high output of quality herbage over a 6-year period without the aid of fertilizer N. They further demonstrate that following decline in red clover content, both herbage yield and quality

A field investigation was carried out over 3 years to determine if there was a synergistic effect on total or seasonal yield when cultivars of perennial ryegrass were grown in combination. The three cultivars used were Stormont Zephyr, Hora and Perma, representing respectively early, medium late and late maturing groups. Each cultivar was grown as a pure stand and also as a 50:50 mixture with each of the other two cultivars. Each of these swards was maintained under two rates of nitrogen fertilization (300 and 600 kg per ha per annum) and under two harvesting treatments (4 and 8 harvests per annum). Mixture yield did not exceed significantly the pure sward yieid of the highest yielding component. Occasional yield improvements were detected for the mixtures averaged as a group over monocultures averaged as a group. There was a tendency, especially under frequent cutting, for the yield response to nitrogen to be greater from mixed than from pure swards.