Renovation of pastures containing paspalum 1 . Persistence of overdrilled ryegrass and prairie grass and effect on seasonal pasture production

Abstract

The persistence of Nui ryegrass and Matua prairie grass was measured over a 2-year period, after over drilling into pasture containing paspalum. Ryegrass and a mixture of rye grass and prairie grass were direct drilled in autumn through triple disc or chisel coulter assemblies. Half the width of each main plot received paraquat in 40 mm bands covering the drill lines while the other half did not. The plots were rotationally grazed by dairy cows. Ryegrass and prairie grass seedlings were tagged, and sequential growth measurements (tiller number and length) were made during each plant's life cycle. Losses (30 – 40%) of plants were highest in the summer following their introduction, and by the end of the study were higher for prairie grass (83070) than for ryegrass (65%). Twenty percent of total losses were ascribed directly to ‘animal effects’ mainly plant removal (‘pulling’), and these were higher for prairie grass than for ryegrass. Coulter type and band-spraying of paraquat had no effect on plant survival. Species mixture had inconsistent effects. Large plants (20 – 30 tillers) had a higher probability of surviving over summer than did small plants > 10 tillers). The high losses of introduced plants was reflected in only small ( < 500 kg/ha), short-term (abou16 months after drilling) improvements in pasture production. Practical suggestions are made for improving the survival of over drilled species and these are examined in subsequent papers.

Keywords:

• pasture renovation
• overdrilling
• Lolium perenne
• Bromus willdenowii
• Paspalum dilatatum
• competition
• persistence
• pasture production
• grazing damage
• dairy cattle