Grain maize

In the descriptive table, the varieties are classified according to earliness (precocity), which is calculated according to the moisture content in the grain at harvest.

The varieties are divided into 4 maturity groups:

• Very early varieties
• Early varieties
• Semi-early varieties
• Semi-late varieties

For a general recommendation, a variety must achieve a score for lodging resistance and stalk rot of at least 7 (± 8% lodged plants or plants affected by stalk rot in the tests followed). When the scale of 1-9 is used, 9 indicates the most favorable rating.

The following minimum standards were used for the grain yield (in relative figures) and earliness:

1. Very early varieties
   earliness (abs.): < 26.9%
   grain yield (rel.): ≥ 94%
   
   
2. Early varieties
   earliness (abs.): between 26.9% and 28.5%
   grain yield (rel.): ≥ 97%
   
   
3. Semi-early varieties
   earliness (abs.): between 28.5% and 30.2%
   grain yield (rel.): ≥ 100%
   
   
4. Semi-late varieties
   earliness (abs.): > 30.2%
   grain yield (rel.): ≥ 104%
   
   

Concerning the length of the plants, the height of the cob formation, the grain yields (converted to a moisture content of 15%) and the cob yield, the results are expressed as a percentage of the average of all varieties included in the Belgian variety list.

Earliness (precosity)

Grain maize is grown for the dry grain. In connection with the drying costs, the aim should be the lowest possible moisture content of the grain (maximum 35% – 36% moisture). When comparing two varieties with at least 1% difference in moisture content in the grain, the variety with the highest moisture content must achieve at least 2% more grain yield per % moisture difference in order to equal the economic value.

Grain yield

The grain yield is strongly variety-specific, but is also influenced by the year, location and time of sowing. The grain yield is usually inversely proportional to the earliness level.

Lodging resistance

Because the crop usually remains in the field until late autumn, the lodging resistance must be good (rating of at least 7). Lodging is usually caused by root weakness, but sometimes stem weakness can be a major cause. Root weakness occurs in both short and tall breeds. When lodged by stem weakness, the green stems break or kink about one meter above the ground.
Stem weakness differs from stem rot, in which the weak stem base buckles. Plants that are lodged at more than 10% at the time of harvest are generally regarded as objectionable.

Use of grain maize varieties for CCM and CCS

Wet grain maize (CCM) is harvested at a dry matter content of about 60%. Sometimes, in addition to grains, a limited part of the spindle is also harvested. The entire product is ground and can be stored well by ensiling. If the dry matter content is less than 50%, grinding can cause problems.

For corn cob silage or CCS, the entire cob (cob + spindle + bracts), the cob stem and sometimes a piece of the stem and/or some leaves are harvested. The time of harvesting is less dependent on the dry matter content than with grain maize or CCM.
When choosing varieties for CCM and CCS, approximately the same criteria apply as for grain maize, but varieties with a lower early maturity (category semi-late to late) are certainly not disadvantageous. In addition, the spindle proportion and the cob yield (grain + spindle) are important. These two characteristics are calculated based on the fresh mass.

Stalk rot

Stalk rot mainly occurs in a ripening crop or in a crop that has died due to drought or night frost. Typical symptoms are weak stem feet, which often bend over, and (often) drooping cobs. Great cob losses can occur during harvest. Good stalk rot resistance is important if the harvest of a mature crop has to be postponed for several weeks due to bad weather conditions.

In addition to an assessment in the yield trials, stalk rot resistance is monitored in separate trials (from the beginning of October to the end of November). The evolution of the stalk rot infestation can be determined from these data. This is important for flexibility in the harvest.

Common smut

Infestation by common smut mainly occurs in dry summers and mainly affects the cobs. Resistance to this fire fungus is more important with grain maize than with silage maize. More than 5% common smut is detrimental to the yield.

Helminthosporiosis

A leaf spot disease caused by the fungus Helminthosporium has been observed in maize cultivation in Belgium. There are currently 3 known species: H. turcicum, H. carbonum and H. maydis, the first of which is the most common in Belgium. The fungus mainly develops in humid weather and temperatures between 20 and 25°C. Infection occurs through contaminated crop residues in the soil and the spread of the spores via the wind.

The symptoms of H. turcicum are large gray-brown spots up to 15 cm long. The spots are enclosed by a dark brown seam. The lower leaves are infected first and then the upper leaves. Eventually the spots merge and large parts of the leaf can die. In H. carbonum and H. maydis there are many spots of only 2 – 3 cm long.

The fungal infestation leads to a reduction in yield and if the infestation is already observed before or during flowering, the grain yield can be up to 50% lower. In addition, it leads to a reduction in the feed value (starch content and cell wall digestibility) and ensilage problems. Threshing grain maize can also be made more difficult (not getting rid of dried grains).

Possible measures to prevent the disease are clean seed, tolerant varieties and good and deep incorporation of crop residues. There are large differences between the breeds in terms of tolerance to helminthosporiosis. This leaf spot disease has been monitored since 2007 in official variety trials. As soon as information about all recommended varieties is known, these will be included in the variety list.

Early growth and cold sensitivity in spring

For the highest possible yield, a crop with good early growth is required. The yield can be strongly influenced by the seed quality, but there is also a clear influence of variety.

Varieties with an early development reach full ground cover sooner than the slower varieties. A variety with a low rating for early growth is preferably sown more densely for April sowing. As with silage maize, ILVO is studying the cold sensitivity of the varieties in spring.

Length of the plant and height of the cob settlement

The choice of plant type can be important for the firmness of the variety. Tall varieties with a high cob setting are usually more prone to breaking or kinking the stems; this can result in a significant loss of yield (cobs matured too quickly and crop losses).

Field and variety selection and stand density

The desired moisture content of the grain is about 10% lower than with traditional silage maize. That is why it is important to be able to sow early and harvest late. The plot can be used both early and late in the season is a major asset. High demands must be made on the moisture supply, since the grain formation and the grain yield react strongly to moisture deficiency, especially during the flowering period. The structural condition of the soil must be optimal; waterlogging can cause both flooding and water shortage. Soils that are sensitive to night frost are also not suitable for growing grain maize.

In the case of grain maize, in addition to the grain yield and the moisture content of the grain, the bearing strength and resistance to stem rot are of great importance. Timely sowing is very important for early maturity and grain yield; if possible, sow around April 20. Late sowing (after 5 May) is detrimental to the yield and ripening. The most appropriate stand density is 80,000 to 90,000 plants per hectare. At a higher stand density, the bearing strength and grain maturation are usually adversely affected and the cob formation is poorer. With an average field emergence of 85 to 90%, a sowing of 95,000 to 105,000 seeds/ha is thus desirable.

For small varieties, however, a higher standing density usually leads to a higher yield. If such varieties have good lodging resistance and good resistance to stem rot, it makes sense to increase the sowing density to 110,000 - 120,000 grains/ha to arrive at a planting number of 100,000 - 110,000 plants/ha. Sometimes silage maize varieties are used for grain maize. In general, they are less suitable than grain maize varieties described above.

In connection with the choice of varieties and the cultivation method, it is very important to determine before sowing whether ready-to-use or grain maize will be grown. If the choice cannot be made in advance, it is advisable to focus the selection of varieties and cultivation on grain maize.