This section provides information on how the trials were
conducted and describes the performance characteristics reported in the results tables.
Trial Management Details
The results presented in these webpages are a compilation of a series of ten
annual trials, cycled between three sites; near Dromore Co Down (54°26'N, 6°10’W), near Comber Co Down
(54°33’N, 5°45’W) and on the trial grounds at Crossnacreevy (Gransha) (54°32’N, 5°52’W). Since
1997, varieties have been tested under the standard ‘open establishment’ system. Since 2001 a
plastic mulch system has also been used. Not all varieties are tested under both management systems,
as later silking types need plastic mulch to fully mature in N. Ireland. Conversely, very early maturing
but potentially lower yielding types are not economic under plastic.
- Trial plots: The 14m long trial plots comprise four
rows at an average spacing of 75cm. Three replicate plots are sown under each management. To
avoid edge effects between varieties, only the two central rows are harvested.
- Sowing details: A sowing rate of 100k seeds/ha is used for all varieties
with a seed spacing of 13cm and a sowing depth of 3.5cm.
- Sowing and harvest dates: The trials are always sown as soon as possible
after soil temperatures reach around 10OC, which is normally during the last
week of April or the first week of May. Harvesting is timed on the basis of a target 30% dry matter
content averaged across all the varieties. This means that the plastic mulch system is harvested
in mid October, while the open established plots are allowed to grow on, normally until growth ceases
at the end of October or early November.
- Fertility and weed control: The application of fertiliser is modified
depending on whether farmyard manure or slurry has been applied to the trial site. Following soil
analysis, the final levels of nitrogen, potash and phosphate that are applied are consistent with RB209
guidelines. In the open system part of the nitrogen and if required the phosphate, is delivered
‘down the spout’. Pre-emergence herbicides under plastic contain the active ingredients: Bromoxynil;
Flufenacet; Isoxaflutole; Terbuthylazine and a mineral oil adjuvant (wetting agent). Open trials
have post emergence herbicides applied six weeks after sowing and contain the active ingredients Mesotrione,
Terbuthylazine and Bromoxynil with a mineral oil adjuvant. Additional broad-leaf weed herbicides
are applied as necessary in compliance with manufacturers’ directions.
- Plastic film: The film used is a 6µm perforated photodegradable plastic
applied over rows 1 & 2 and rows 3 & 4 of the 4-row plots.
Measured
characteristics
A range of performance characters are noted during the growing of the crop or assessed
on the harvested herbage as follows:
- Silking date: This is the average date on which each
variety produces its female flowers, called silks. This is an important agronomic date as it is
not until these silks have been fertilised by pollen from the male ‘tassel’ flowers, that cob filling
can commence.
- Silking height: This is height of plants at silk emergence, measured
in centimetres to the base of the tassel and expressed +/- the control height of 1.8m.
- Total yield: This is the total dry matter yield in t/ha produced by
each variety and is presented in the tables as a percentage of the control yields.
- Dry matter content: This is the percentage dry matter of the harvested
material and is an important characteristic as it indicates the degree of maturity the variety managed
to achieve by the time of harvest. Varieties failing to reach at least 25% DM can be expected
to have an effluent loss risk and may not be suitable for more marginal locations or for growing in
Northern Ireland without plastic.
- Starch production: The amount of starch produced in the total harvested
material is presented as a percentage ‘Starch Content’ and as a ‘Starch Yield’ (calculated as a percentage
of the control yield in t/ha). This is an important indicator of the feeding value of the harvested
material, especially when being fed as a supplement to a mainly grass silage winter feed or as a buffer
feed to stock grazing spring grass.
- Metabolisable energy: This is a measure of the total energy produced
by the crop and is presented as a percentage ‘ME Content’ and as an ‘ME Yield’ (calculated as a percentage
of the control yield in t/ha). This is an important indicator of the animal value of the crop,
which is particularly important when forage maize silage is the primary winter feed.
- Additional
Characteristics: The trials are regularly monitored throughout the growing season
and observation notes taken on visible characteristics of agronomic value. These include lodging, brackling, disease infestation, early vigour, cob ripeness and any other exceptional
growth responses. In addition, total digestibility and organic matter are analysed on the harvested crop.
