Renovation of pastures containing paspalum 2. Effects of nitrogen fertiliser on the growth and persistence of overdrilled ryegrass

Abstract

The effects of nitrogen fertiliser on the growth and persistence of ryegrass seedlings transplanted into plots with high or low levels of paspalum were investigated in two field experiments over successive years. Ryegrass seedlings were introduced in July of each year, simulating autumn overdrilling, and were permanently identified. Rates of nitrogen varied from 48 to 67 kg/ha and were applied between August and October. Plots were grazed by cows at intervals. Half the plots were covered by wooden cages during each grazing and were defoliated by clipping. These experiments confirmed the high summer losses of introduced ryegrass plants as previously reported. Large growth responses to nitrogen fertiliser (50 -350070 for herbage dry weight, tiller length, tiller number) by the introduced ryegrass were obtained, but these were insufficient to improve survival. The effects of grazing interval, climatic stresses, competitive resident species, cow damage during grazing, and the presence of paspalum were also considered to influence ryegrass survival.

Survival of endophyte-free perennial ryegrass after autumn spray/ drilling in the Waikato

“…The pattern of high losses of newly sown endophyte-free ryegrass plants during the first summer/ autumn mimics that for high endophyte ryegrass (Thom et al 1986b;Thom et al 1993). However, pulling made a greater contribution to losses than was reported by Thom et al (1986a). Exceptionally dry and warm weather in summer/autumn 1998 continued the pattern of losses to levels of about 200-250 plants/m 2 , which were similar to stable plant numbers in other dairy pastures established by spray/drilling (Thom et al 1993).…”

“…Tillering of seedlings is essential to their survival (Jewiss 1972), and a plant's ability to do this depends on availability of light and nutrients. Eliminating competition for these factors at the time of sowing aids establishment of ryegrass swards (Thom et al 1986a). Double spraying with glyphosate before sowing in autumn greatly reduced volunteer plant density, increasing the survival of sown plants (van Vught & Thom 1997).…”

Growth and persistence of perennial ryegrass lines with different tolerances to "pulling" during grazing

“…Standard procedures (Thom et al 1986) were used to determine the botanical composition of herbage collected from main plots in February, April and July 1995 (Period 1) and from subplots in September and December 1995, and March 1996 (Period 2). Ryegrass and Poa spp. tiller densities were estimated on 3 occasions from tiller counts in 2 randomly positioned frames (20 × 5 cm) per plot in Period 1, and in 2 frames per subplot in Period 2.…”

“…During recent testing of further selections from the Mangere ecotype at four Waikato sites, a wide range of tolerances to "pulling" or the physical removal of clumps of ryegrass plants (plus 2-5 cm of roots) from the sward by cows during grazing was noted, suggesting a genetic component to the ryegrass pulling phenomenon. Losses of grass plants or tillers have often been associated with cattle grazing in summer-autumn (Hughes & Jackson 1974;Thom et al 1986) and some researchers have correlated increased pulling with increased use of nitrogen (N) fertiliser (Mitchell & Dickens 1979;Tallowin et al 1986). Many explanations of ryegrass pulling have appeared in the popular press (e.g., Anon 1992), but the relative importance of pulling to sward tiller density, herbage accumulation and persistence is not well defined for intensive dairying systems.…”

Changes in yellow bristle grass (<i>Setaria pumila</i>) abundance after drought implications for pasture management

“…Summer drought, combined with high evaporation levels will severely limit ryegrass persistence (Waller & Sale 2001). Thom et al (1986a) also concluded that summer temperatures and dry periods in Waikato may lead to restrictions in ryegrass growth, survival and competitiveness, even in non-drought years. They found that high ryegrass losses occurred over summer (Thom et al 1986b).…”