by David Chapman, DairyNZ

Pasture potential

Kowhitirangi Monitor Farm

Variability in pasture growth

Feed supply/demand curve (rough!!)

What is ‘persistence’ (longevity) in perennial ryegrass?

Pasture choice options

Perennial ryegrass

• Heading date
  • ‘mid’ season – like the old Nui type
  • ‘late’ season – 2 – 2 ½ weeks later than mids
  • ‘very late’ season – 2 ½ – 3 ½ weeks later than mids
• Ploidy
  • Diploid
    • Mids, lates and very lates all available
  • Tetraploid
    • All basically late or very late heading
  • Endophyte
    • It’s complicated ….!

Some general points

• Diploids generally more persistent than tetraploids – greater tiller density, more tolerant of pugging etc.
• Later heading diploids generally grow a bit more feed than mid season – but shift the feed supply, more in summer and autumn, lower spring peak.
• Tend to sit at the top of the FVI for this reason.
• Later heading diploids have slightly better quality than mid-heading – additional 0.1 – 0.2 ME, fewer tillers go reproductive in spring.
• Later heading diploids compete more strongly with clover – lower % clover in the pasture than mids.

Other species

Grasses

• ‘Short rotation’ ryegrasses
  • True annuals – winter feed (Hogan, Zoom, Progrow, Tama)
  • Italians – ~ 2 years (more under excellent conditions) (Tabu, Asset, Feast, Moata)
  • Hybrids – cross between perennial and annual, 2-3 years (Shogun)
• Tall fescue (perennial)
  • Well-adapted to heavy soils
  • Tolerates waterlogging better than ryegrass
  • Good for hot, dry climates
  • Summer-active and summer-dormant types available
  • Quality OK if keep on top growth rates – spring is the risk period
  • Persistence can be better than ryegrass if used in the right places
• Cocksfoot (perennial)
  • Highly persistent (generally)
  • Drought tolerant
  • Tolerant of lower soil fertility
  • Summer growth is good, winter/early spring can be slower than ryegrass
  • Newer varieties much less likely to go clumpy and rank than old types
• Also-rans in the grasses
  • Not many worth considering ….

Legumes

• White clover
  • Under-valued for its contributions
  • Suppressed by high N fertiliser rates
  • Can increase total annual DM by 1-3 t DM/ha when contributing 30% of total pasture DM in summer
  • Great feed quality (but potential bloating)
  • Fixes N: ~ 60 kg N/tonne clover DM grown. E.g. if growing 10 t pasture, 20% clover (= 2 t) = ~ 120 kg N fixed, ½ of which is transferred to grass
  • Clover content is highly variable – year-to-year: hard to rely on fixed N for grass growth
• Red clover
  • Short-lived perennial (3-4 years)
  • Summer active, deep tap root
  • Low winter/early spring growth
  • Great quality feed (like most of the legumes)

Herbs

• Plantain (‘narrow-leaved’ plantain)
  • Short-lived perennial
  • Stout tap-root, plus fibrous roots
  • Summer active
  • Winter growth better in new cultivars (Tonic)
  • Generally very high feed quality
  • Can use in mixtures with grass, or as monoculture crop
  • Beneficial for reducing nitrate leaching – diuretic, plus soil nitrification inhibition?
• Chicory
  • Short-lived perennial
  • Strong tap-root, no fibrous roots
  • Summer active
  • Highly susceptible to grazing damage under wet soil conditions – crown rots etc
  • ‘Rocket fuel’ in terms of animal production