Factors influencing survival of strains of ryegrass during the summer

Simulated swards forming a replacement series of the ryegrass cultivars 'Grasslands Manawa' and 'Grasslands Ruanui' consisting of two monocultures and three mixtures were cut during establishment to two heights and at two frequencies. The cutting frequencies were continued for a year after the first cut, after which all swards were cut uniformly until the experiment was concluded 2 years after sowing.Yields, tiller numbers, and plant survival were recorded separately for the cultivars. These data were used to fit parameters to the twospecies competition model of de Wit (1960).Manawa was initially dominant in all cutting systems, and this dominance was greatest where cutting was infrequent. Initial lax cutting reduced the suppression of Ruanui. The suppression of Ruanui during establishment is largely attributed to shading by Manawa, and where hard cutting removed stubble, Ruanui tiller numbers were reduced and Ruanui plants died in the mixtures with Manawa. This effect hindered the transition to dominance of Ruanui in the summer and autumn after sowing.The results indicate that mixing of the cultivars would be advantageous as a function of both herbage yield and quality under the frequent lax cutting system, because the cutting did not markedly suppress Ruanui initially, allowing Ruanui to contribute substantially to the yields of the mixtures in the post-reproductive period when yields of Manawa were low. With infrequent hard cutting the yield contribution of Ruanui in mixture during the post-reproductive period was small and, because Manawa was unable to utilise the space made available by the death of Ruanui plants, depressed yields from mixing were observed. It is concluded that no advantage is gained by mixing Ruanui and Manawa where the management system in the first year tends to maximise the yield of Manawa.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Competition among pasture plants

Harris

Thomas²

1970

“…High productivity and good persistence of Italian ryegrasses in Southland (Armstrong 1981) contrasts with other environments in New Zealand (Percival et al 1989;. In other regions, Argentine stem weevil damage is greater, summer moisture stress is more severe and occurs more frequently, and summer temperatures are higher, all factors that greatly reduce plant persistence of Italian and hybrid ryegrasses (Lucanus et al 1960;Harris 1970;Hume 1993).…”

Section: Ryegrass Productionmentioning

confidence: 99%

“…This was most probably linked to the infrequently grazed pastures reaching ceiling yield before grazing (Scott 1976) and suffering senescence as a result of excessive herbage accumulation (Brougham 1956;Hickey & Baxter 1989). Italian and hybrid ryegrasses generally require infrequent grazing for high productivity and persistence, particularly during periods of high temperatures and low soil moistures in summer (Mitchell 1954;Lucanus et al 1960;Brougham 1960Brougham ,1961. However, considering the importance placed on producing high-quality summer pastures in Southland, desirable grazing management strategies may include more frequent grazing to maximise pasture quality rather than yield.…”

Section: Grazing Frequencymentioning

confidence: 99%

Evaluation of seven Italian and hybrid ryegrasses under sheep grazing in Southland, New Zealand

Hickey

Hume

1994

Three Italian and four hybrid ryegrass cultivars (Lolium multiflorum and L. boucheanum Syn. L. hybridum) sown with the white clover cultivar Grasslands Huia (Trifolium repens), were evaluated under frequent/hard grazing or infrequent/ lax grazing. Dry matter (DM) yields and species composition were assessed for 5½ years. Ryegrass tiller and white clover growing point population densities were determined annually, and leafrstem ratios every spring and autumn. Ryegrass tillers were assessed for infection with an Acremoniumlike endophytic fungus and bacterial wilt disease (Xanthomonas campestris pv. graminis). The Italian ryegrass cultivars Moata and Concord had total yields 33% greater than the mean of the other cultivars (1800 kg DM/ha) over the first autumn and winter. The Italian cultivars persisted well for 3 years, except Concord which had a high incidence (34%) of bacterial wilt. Of the hybrid ryegrasses, cultivar Corvette had high ryegrass yields in the first year (9800 kg DM/ha), similar to those of the Italian cultivars, and continued to be high-yielding and persistent throughout the experiment. However, its degree of aftermath heading was high and probably reduced ryegrass herbage quality in summer and autumn. An inverse relationship between ryegrass yield and white clover yield resulted in few significant differences in total yields between cultivars. Infrequent/lax grazing maximised total annual yields (+5%) but decreased white A94044 Received 21 April 1994; accepted 4 August 1994clover yields (-13%). With the importance placed on achieving high white clover growth in the cool temperate environment of Southland, choice of ryegrass cultivar should consider factors such as pasture quality (primarily percentage composition of white clover), tolerance of the cultivar to a range of grazing managements, and seasonal herbage production. The presence or absence of endophyte was not considered a major factor influencing the long-term persistence or productivity of the cultivars evaluated at this site.

“…Under dry summer conditions, perennial ryegrass tends to become dormant and there is a delay of 2-3 weeks between the onset of effective autumn rains and the beginning of new tiller formation (Silsbury 1964). Lucanus et al (1960) showed that the survival rate of perennial ryegrass over the summer was reduced by low soil moistures and high temperatures. Survival was further reduced if soil N was at a high level.…”

Section: Methodsmentioning

confidence: 99%

Seasonal variations in salinity of soils supporting different levels of barley grass (Hordeum murinum L.)

Popay¹,

Sanders

1982

'Measurements of soil salinity taken throughout the year from barley grass sites and nearby areas showe~ .that s~inity le.vels tend to.be high in soils where barley grass ,?ccurs an~ that sahmty vanes conSIderably dunng the year, reaching particular~y ~ugh It:vels In the late summer on barley grass sites. It is suggested that this high sahmty senously affects the survival of perennial pasture species over the summer whereas barl.ey.grass, being an annual, avoids these adverse growing conditions and can readIly Invade the bared areas in the autumn.