Temperature and cutting effects on the growth and competitive interaction of ryegrass and paspalum

Abstract

The effects of temperature regime, transfer between temperature regimes, and cutting frequency on the competitive interaction of ryegrass and paspalum over 24 weeks were analysed using the de Wit (1960) model of two-species competition. Because of more rapid establishment ryegrass was initially the dominant grass under all treatments. At high (24°C day/18°C night) temperatures, paspalum became the dominant grass where cutting was frequent (2-week intervals), but ryegrass remained dominant where cutting was infrequent (4-week intervals). At low temperatures (14°C day/8°C night) ryegrass was strongly dominant, particularly with infrequent cutting. When transferred from high to low temperatures at 12 weeks ryegrass rapidly increased its competitive power relative to paspalum. Because of marked suppression at low temperature under infrequent cutting paspalum showed a slow increase in competitive power after transfer from 18w.to high temperature, but under frequent cutting paspalum became dominant by the end of the experiment. Cutting more frequently and closely at temperature transfer reduced the dominance of ryegrass and aided the increase in competitive power of paspalum after transfer from low to high temperature. Increase in competitive power was generally associated with an increase in the number of tillers per plant. Ryegrass showed an increase in yield per tiller with decreasing ratio of ryegrass in the sward, irrespective of its competitive situation. The competitive interaction of ryegrass and paspalum produced transgressive overyielding, particularly where a change of dominance between the grasses was emphasised by transfer between temperature regimes and frequent cutting. Differing growth rhythms and enhanced light use efficiency appeared to be the important causes of transgressive overyielding. It is concluded that realisation of the higher yield and stability of ryegrasspaspalum mixtures requires particular environmental and management conditions.

The response of simulated swards of perennial ryegrass and white clover to enriched atmospheric C02: Interaction with nitrogen and photosynthetic photon flux density

“…In subsequent analysis, the results from harvests 3 and 4 have been combined. Growth rates of the pure swards were similar to other published rates for swards (Masterson & Sherwood 1978;Harris et al 1981). The mixed sward had a significantly higher growth rate than the pure swards (Fig.…”

“…One important nutrient, nitrogen, can be either supplied in fertiliser applications or through nitrogen fixation by the clover -rhizobium symbiosis (Ball & Field 1982). Regular cutting can also exert strong pressures on the competitive ability of the sward components (Harris et al 1981). We do not know of any papers on the response of swards under simulated grazing, regardless of composition, to increased CO 2 .…”

Sowing date and nitrogen supply determine the outcome of competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the Pampas region of Argentina

“…Competition between dallisgrass and perennial ryegrass ( Lolium perenne ) is influenced by temperature. Dallisgrass is a stronger competitor than ryegrass at higher temperatures (24/18°C) and ryegrass was a stronger competitor than dallisgrass at lower temperatures (14/8°C) (Harris et al. , 1981).…”