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Early varieties are called flint and late varieties are called dent. In Ireland flint-dent varieties are used which are a combination of both and therefore display hybrid vigour. Early varieties require a shorter growing season and reach maturity much quicker so the chances of frost damage are reduced. They also have a higher starch content and a higher DM if they have to be harvested earlier. If drilling is delayed, early varieties have a far greater chance of reaching maturity at harvest. Usually less effluent is produced when early varieties are ensiled. Late varieties usually have a lower starch content and a lower DM yield. For growing late varieties, lower seed rates are often recommended to enable the crop to reach an ensileable DM percentage. Therefore, increases in yields do not always materialise. If such a variety has to be harvested before maturity is reached, silage production may involve huge drawbacks. This is because it is wetter and therefore more acidic and the fibrous fraction, which stimulates rumen activity, will not be developed. Immature maize will also not produce a high starch silage and therefore the majority of energy will come from sugars rather than starch. It is the starch that is responsible for an increase in milk yields and liveweight gains though.
Early vigour is variety dependent and not related to maturity. Two varieties that display early vigour are Avenir and Kingdom.
Disease resistance does not depend on variety.
Andante
Very good yield and starch content.
Good dry matter content.
Early maturing.
Consistent performer.
Suitable over a wide range of growing conditions.
Good lodging (when the head of the corn drops) resistance.
Origin: The Netherlands.
Avenir
Very good yield and starch content.
Highest dry matter content.
Matures earliest so can be harvested earlier as well.
Consistent performer.
Suitable over a wide range of growing conditions.
Origin: France.
Crescendo
Good yield and starch content.
Good dry matter content.
Early maturing.
Suitable for good growing conditions only.
Origin: The Netherlands.
Hudson
Good yield and starch content.
Good dry matter content.
Early maturing.
Consistent performer.
Suitable over a wide range of growing conditions.
Origin: The Netherlands.
Loft
Highest yield and very good starch content.
Good dry matter content.
Early maturing.
Consistent performer.
Suitable over a wide range of growing conditions.
Origin: Germany.
Melody
Good yield and starch content.
Good dry matter content.
Early cob maturity.
Consistent performer.
Prone to lodging.
Suitable over a wide range of growing conditions.
Origin: The Netherlands.
Tassilo
Very good yield and starch content.
Very good dry matter content.
Early maturing.
Suitable for good growing conditions only. This variety will not grow in stressful conditions.
Origin: Germany.
When choosing a variety it is important not base the selection on yield as a high yield results in a lower starch content. Also, it is recommended to only use varieties that are on the List of Recommendation. In choosing a variety, local knowledge is invaluable.
The main factors to consider are:
1. Time of flowering
2. Cob height
3. Husk cover
4. Stand ability
5. End use
6. Isolation
Under conditions of adequate soil moisture, mid to slow maturing varieties will produce a higher yield than quick maturing varieties. Therefore, if a maximum yield is desired, growers should consider a mid to full season maturity hybrid.
Cob height tends to be closely related to maturity. Varieties that require a longer season usually have higher-set cobs than quicker-maturing varieties. Excessive cob height (greater than 1.5 m), however, can be a contributing factor to lodging especially if there is wind and rain around flowering time, and if stalk rot has infected the plants. Lodged plants can slow harvesting and reduce yield.
Husks function to prevent damage caused by larvae, reduce ear and kernel rots, and protect the grain from weathering. Therefore, a good husk cover (including tip cover) can be important if insects, disease, and pre-harvest rain are likely to pose threats.
Stand ability (resistance to lodging) is important because it reduces harvest losses and grain damage. Many factors contribute to stand ability including resistance to stalk rots, good mechanical stalk strength and cob height. Most modern varieties have good stand ability.
Varieties generally have specific grain characteristics, which govern their suitability for particular end uses such as milling, stock feed, or silage. Therefore, it is important to choose the appropriate variety depending on what the crop will be used for.
All white, waxy and popcorn varieties of maize must be grown in isolation from other maize varieties. This is because pollen from other crops will affect the quality of grain produced by these types.
Isolation guidelines are as follows:
Maize crops planted at similar times need to be separated by a minimum of 200 m.
Maize crops must be planted at least 6 weeks apart to avoid cross-pollination.
Seed companies or grain purchasers may have specific recommendations that need to be followed.
It is not necessary to change the variety from year to year if the one used proved to be successful and is listed on the List of Recommendation.
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