T. A. Williams

The effect of cutting and intensive grazing managements on sward components of contrasting ryegrass and white clover types when grown in mixtures

A field experiment was established at the Institute of Grassland and Environmental Research (IGER), Aberystwyth, to compare the seasonal growth and annual yields of two white clovers when grown with each of five perennial ryegrasses. Swards were subjected to two contrasting defoliation managements, namely cutting only and continuous grazing with sheep. In addition to data recorded on dry matter yields of the swards, the effect of management on growth and development of white clover stolons and tillering of ryegrasses was also studied in the third harvest year. The management of the swards had a significant effect on ryegrass tiller number and on the ingress of weed grasses. Differences in persistency and tillering among the ryegrasses were significantly greater when continuously grazed by sheep than when swards were cut. It is argued that ingress of weed grasses under grazing could be used as an indicator of ryegrass persistency. Among those studied, only two of the ryegrasses were able to provide dense persistent swards under continuous sheep grazing. The white clovers included in this experiment differed in leaf size with Gwenda smaller than Ac 3785. Greater differences existed between white clover components when grazed than when under cutting management. Under continuous sheep grazing there were large differences between the clover varieties in stolon length, stolon weight, number of growing points and root weight. The data indicate the importance of the persistence of mixture components under continuous sheep grazing and, since ryegrass is the main component of a clover/grass seed mixture, greater emphasis in breeding and evaluation programmes should be given to persistence, especially under grazing.

Long-term performance of white clover varieties grown with perennial ryegrass under rotational grazing by sheep with different nitrogen applications

Williams, T. A., Evans, D. R., Rhodes, I., Abberton, M. T. (2003). Long-term performance of white clover varieties grown with perennial ryegrass under rotational grazing by sheep with different nitrogen applications. Journal of Agricultural Science, 140, (2), 151-159. Sponsorship: DEFRA

Forage yield and quality interactions between white clover and contrasting ryegrass varieties in grazed swards

The impact of white clover on seasonal yield and nutritive value traits in perennial ryegrass was investigated using six ryegrass varieties which expressed contrasting levels of water soluble carbohydrate (WSC). These were sown in an upland environment at Syfydrin, near Aberystwyth, in mixtures with white clover and in monocultures. Plots were grazed by sheep and sampled during 1991-93. Grass yields in mixtures and monocultures were similar except during mid to late summer when clover contents were high. White clover had a considerably lower WSC content but a much higher crude protein (CP) content than the ryegrasses. The WSC content of grasses in mixed swards was consistently lower than in monocultures and markedly so during mid to late summer. Use of ryegrass varieties with a relatively high WSC content can compensate for this depletion. Consequently high WSC grasses may reduce the amounts of nitrogen excreted by ruminants grazing mixed swards by increasing the efficiency of protein use from clover.

Quality characteristics of backcross hybrids between Trifolium repens and Trifolium ambiguum

Two generations of novel backcross hybrids between white clover (Trifolium repens L.) and the related species Trifolium ambiguum,with white clover as the recurrent parent, were analysed for forage quality characteristics. Water soluble carbohydrate (WSC) levels, nitrogen concentrations (%N), and dry matter digestibility (DMD) were recorded for the hybrids and parental species grown in deep soil bins with and without a companion grass. Half the experimental material was subjected to moisture stress by being left unwatered through the four-week period when measurements were made. Four such four -week cycles of drought were imposed. The first and second generation backcrosses had the highest values for WSC, but were lowest for N%. There was no difference between the different legume lines (parents and backcrosses) for DMD. No effects of either moisture stress or presence of a grass companion on quality traits were observed. The WSC and %N of the grass component differed significantly depending on which legume line it was grown with. The importance of these results for the potential use of these hybrids in agriculture is discussed.

Residual N effect of grazed white clover ( Trifolium repens )/ryegrass ( Lolium perenne ) swards on subsequent yields of spring barley

Residual nitrogen from white clover/ryegrass swards and ryegrass monocultures was quantified in terms of the barley yield obtained after ploughing the swards. Clover/ryegrass swards based on small and medium-leaved cultivars of white clover and ryegrass monocultures were grazed continuously by sheep for 3 years (1984–87) at the Welsh Plant Breeding Station, Aberystwyth, ploughed in the following spring (1988) and then sown with the spring barley cultivar Doublet. Yield of barley obtained after clover/ryegrass mixtures was 50% greater than barley harvested after ryegrass monocultures. Barley yield was 1·6 t/ha more following the white clover cultivars Gwenda and SI84 with ryegrass than following ryegrass monocultures.