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 – 350% 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.

Keywords:

• pasture renovation
• Lolium perenne
• Paspalum dilatatum
• competition
• persistence
• nitrogen fertiliser
• seasonal growth responses
• grazing damage
• dairy cattle