Variety trials are sown annually at the AFBI Plant Testing Station,
Crossnacreevy in mid-summer, and evaluated over three growing seasons.
- Perennial Ryegrass trials are grazed with cattle in
the fi rst year and measurements are taken during the second and third years to assess long-term potential.
Perennial Ryegrass and Timothy varieties are assessed under
both a simulated rotational grazing management with 320 kg/ha nitrogen applied per annum and under a
3-cut silage management with backend simulated grazing, with 350 kg/ha nitrogen applied per annum.
- Hybrid ryegrass: being best suited to medium-term use, is assessed
over three harvest years under a 3-cut silage management with Spring and backend simulated grazing,
at 425 kg/ha nitrogen applied per annum.
- Italian ryegrass: being best suited to short-term conservation use,
is assessed in both first and second harvest years under a silage management with Spring plus backend
simulated grazing, at 425 kg/ha nitrogen applied per annum.
- White Clover: sown with Fennema perennial ryegrass, is assessed in
the second and third harvest years. Reaction to rotational cattle grazing is assessed using either 50
kg/ha nitrogen applied in Spring (Low N) or 200 kg/ha nitrogen applied throughout the season (High N).
Yield potential is measured separately in a simulated rotational grazing trial at ‘High N’.
Key
to performance tables.
The recommended varieties are grouped into tables according to species and maturity
and are listed within each category in order of heading date or leaf size.
Therefore,
the variety at the top of a list is not necessarily the best.
The parameters
recorded in the tables are as follows:
- Heading date: Indicates the relative maturity of varieties,
recorded when half of a set of individual indicator plants of each variety produce seed heads in an
average season at AFBI Crossnacreevy. Dates are about 4- 6 days earlier than ear emergence in swards
and are not the date of the first silage cut.
- Leaf size: Indicates the relative leaf size of clover varieties as
a percentage of Grasslands Huia.
- Total yield: Total annual dry matter yields (t/ha DM) as a percentage
of the bold type diploid varieties in each table. The tetraploid perennials are expressed as a percentage
of the diploid perennial controls and for Italian and hybrid ryegrasses, all yields are given as a percentage
of the first year control yield.
- Early spring growth: The yield in t/ha DM available by the end of
March at Crossnacreevy.
- Spring growth: The yield in t/ha DM available by the end of April
at Crossnacreevy.
- 2-cut silage yield: The combined yield from the first two silage cuts
as a percentage of the mean of the bold type diploid varieties.
- 2 cut D-yield: The total yield of digestible material produced in
the first two silage cuts.
- Grazing grass quality: The D-value of leafy grazing swards in August
(differences of less than 2% should be treated as not significant).
- Sward density: Assessed at the end of a harvest year on a 0-9 scale
of increasing density. Ratings above 6.0 for diploid and 5.0 for tetraploid ryegrasses indicate a high
level of persistence.
- Grazing density: Indicates the relative tolerance of white clover
to grazing on a 0-9 scale. High values represent good persistence and a potential to proliferate under
a suitable management.
The data in the tables are an accumulation from
a large over-years data matrix from different trials at AFBI Crossnacreevy. The number of years of data
representing each variety depends on its stage in the testing programme.
