Trial management details
The results presented in this booklet are a compilation of a series of ten annual trials, originally sited near Dromore Co Down (54°26’N, 6°10’W), and later near Comber Co Down (54°33’N, 5°45’W) and Carrowdore Co. Down (54°34’N, 5°33’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 10°C, which is normally towards the last week of April. 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 maize is generally 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 fertilizer 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 photodegradable plastic applied over rows 1 & 2 and rows 3 & 4 of the 4-row plots.
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 the height of plants at silk emergence, measured in centimetres to the base of the tassel and expressed +/- 180cm.
- 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.