Silage maize

Precocity - dry matter content (DM content) of the whole plant

The most desirable DM content is achieved with a hard dough grain. The crop then has a DM content of ± 30%. The DM content of the whole plant is an important measure of silage losses. At a DM content of 27% or lower, the silage losses increase considerably.

Global relationship between harvest date, DM content, cob percentage and silage losses in silage maize under normal growing conditions:

The DM content of the whole plant depends on several factors. The time of flowering, the speed of ripening, the share of the cob, the dry matter content of stem and leaf, the degree of damage by stalk rot as well as the weather at harvest influence the final dry matter content of the entire plant.

Under favorable conditions, a late-flowering variety can still achieve a relatively high DM content due to rapid maturation. However, with late sowing, early harvest, slow ripening due to little sunlight or early night frost, the DM content of late-flowering varieties is often disappointing.

When there is a lot of damage from stalk rot, the DM content often shows a strong increase. Varieties with a moderate resistance to stalk rot then have a relatively higher DM content than well-resistant crops, but the quality of the crop to be harvested can drop sharply.

Lodging resistance

Although lodging is not a common phenomenon, quite serious lodging does occur in some years or on certain plots. Especially when the crop has experienced a period of very rapid growth, it is prone to lodging. When the crop is subject to lodging, the stems usually point in the same direction.

Because of the loss of yield and capacity, more than ten percent of lodged plants is considered objectionable. Lodging often occurs especially in late sown crops. Planting too close also leads to slightly more lodging. Lodging is usually caused by root weakness, but sometimes also by stem weakness.

A lack of firmness due to root weakness, where the plants grow crooked or fall over near the ground, occurs in both short and long varieties. When lodged by stem weakness, the green stems break or kink about one meter above the ground; this in contrast to stalk rot, where the weak stem (foot) often bends. Breaking or kinking of the green stem mainly occurs in tall varieties with a high to very high cob setting.

Lodging can occur throughout the growing season. With summer lodging, the crop usually still recovers. However, the characteristic "walking sticks" often remain, which leave a somewhat longer stubble at harvest.

The ratings for firmness are mainly based on the percentage of lodged plants at harvest. Clear varietal differences are expressed here.

Yield

The data for the total DS yield (in relative values) have been calculated against the average of all varieties and are therefore mutually comparable. The DOM (digestible organic matter) is calculated on the basis of the total dry matter yield and the digestibility.

Digestibility

Digestibility is the most important quality characteristic for silage maize. The values in the tables indicate the percentage of digestible organic matter expressed in relative figures to the average of all varieties. It concerns the average digestibility figure of at least 2 trial years with 9 analyses per year. The determinations are made with the NIRS method (Near Infrared Spectroscopy) based on the cellulase method.

The difference in digestibility per kg dry matter (100 = 75.8%) between the most and the least digestible variety is ± 4.7% (abs.).

Variety differences are largely determined by genetic differences in digestibility of the cell wall components. Earliness and proportion also play a role in this. The influence of the year and the field is also important.

Starch

Since starch only occurs in the grain, the starch content of the plant is a good measure for the proportion of the cob. In addition, a high starch content is an indication of a proportionally good ripening.

Silage maize varieties, either early ripening or early sown semi-early varieties with a high starch content, are therefore also suitable for MKS (maize cob meal) or CCM (Corn Cob Mix). This can be useful for farmers who do not yet want to choose the use (silage or MKS - CCM) at the date of sowing.

In this variety list, the results for starch are based on the average of at least 2 trial years with 9 analyses per year. As for the digestibility, the analyses were performed with the NIRS method. The difference in starch content between the varieties is ± 9 units.

The silage maize varieties are classified according to earliness (precocity). For this purpose, the dry matter content of the total plant at the time of harvest is looked at in comparison with a number of reference varieties.

With regard to the values expressed in ratios, 100 is the average of all varieties included in the Belgian catalog of varieties. When the scale of 1-9 is used, 9 indicates the most favorable rating.

In the descriptive list, a selection of varieties is drawn up for different cultivation conditions, taking into account minimum standards per earliness category, for total DM yield, digestibility, DOM yield (digestible organic dry matter yield), lodging resistance and stalk rot resistance.

Within a certain earliness category, the silage maize varieties must, in addition to the minimum standard for lodging resistance and stalk rot resistance:

• Either meet the minimum standard for total DM yield combined with the minimum standard for digestibility;
• Or meet the minimum standard for DOM yield

That means, per category:

1. Very early varieties
   earliness (precocity) (abs.): > 37%
   lodging resistance (1-9): 7.0 (± 8% lodged plants)
   stalk rot resistance (1-9): 7.0 (± 8% affected plants)
   OR total dry matter yield (rel.): 95%
   and digestibility (rel.): 100%
   OR DOM Yield (rel.): 95%
   
   
2. Early varieties
   earliness (abs.): between 34.9 and 37%
   lodging resistance (1-9): 7.0 (± 8% lodged plants)
   stalk rot resistance (1-9): 7.0 (± 8% diseased plants)
   OR total dry matter yield (rel.): 98%
   and digestibility (rel.): 98%
   OR DOM Yield (rel.): 98%
   
   
3. Semi-early varieties
   earliness (abs.): between 33.2 en 34.9%
   lodging resistance (1-9): 7.0 (± 8% lodged plants)
   stalk rot resistance (1-9): 7.0 (± 8% lodged plants)
   OR total dry matter yield (rel.): 102%
   and digestibility (rel.): 97%
   OR DOM Yield (rel.): 100%
   
   
4. Semi-late varieties
   earliness (abs.): < 33.2%
   lodging resistance (1-9): 7.0 (± 8% lodged plants)
   stalk rot resistance (1-9): 7.0 (± 8% diseased plants)
   OR total dry matter yield (rel.): 103%
   and digestibility (rel.): 97%
   OR DOM Yield (rel.): 101%

Stalk rot

Stalk rot (Fusarium sp.) mainly occurs in a ripening crop or in a crop that has died due to issues such as drought or night frost. It can be recognized by the thin stem feet, the often down-hanging cobs and the bending of the thin stems, which often fall in different directions. There can also be quite a bit of cob loss during harvest. At dry matter contents below ±28 % (late varieties), stalk rot usually does not cause any problems.

Common smut

Common smut (Ustilago maydis) mainly occurs in dry summers. If, in particular, the cobs are affected, some yield loss in feed value (VEM, DVE) may occur. In case of heavy infestation, it is recommended to feed the fresh maize silage.

Helminthosporiosis

Recently 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 rise to 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.

Early growth and cold sensitivity in spring

For the highest possible yield, a crop with good early growth is required. This can be strongly influenced by the seed quality, but there is also a clear influence on variety. Varieties with an early development reach full ground cover sooner than the slower varieties. A variety that rates low for early growth is preferably sown a bit more closely in April.

ILVO is performing research on a rapid test to determine the cold sensitivity of the varieties in the spring. Varieties with a good tolerance to cold could be sown earlier so that the growing season of the maize, with possible increase in yield, could be extended.

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 significant crop losses.

In general, the best sowing time for silage maize is between 20 April and 5 May.

On farms where it is possible to sow early (before 1 May), preference should be given to the most productive varieties from the very early and early varieties. High digestibility is a plus for highly productive cows.

Mid-early to mid-late varieties can sometimes give a very high yield. When choosing these varieties, the farmer should be aware of a certain risk of insufficient ripening under less favorable weather conditions in the autumn.

A mid-early to mid-late variety is no longer eligible for sowing after 1 May.

The descriptive variety list for silage maize varieties does not recommend late varieties as no variety meets these standards.

Very early varieties are suitable for late sowing or early harvest. In addition to the total dry matter yield, lodging resistance and digestibility play an important role here.

The most appropriate density is 100,000 plants/ha with sowing until the beginning of May. With an average field emergence of 85 to 90%, a sowing rate of 115,000 seeds/ha is therefore desirable.

For tall, leafy varieties, a higher stand density is often unfavorable because earliness and lodging resistance both decrease and harvest losses increase. With short, less leafy varieties, a higher plant density usually leads to a higher yield. If such a variety is well resistant to lodging, it makes sense to increase the sowing density to 120,000 grains/ha to arrive at a planting number of 110,000 plants/ha.

For several years, strict fertilization standards have been applied in certain areas in Flanders (including in water extraction areas). The availability of adapted varieties with a good yield potential for these areas is the basis for the profitability under such low input fertilization conditions.

Research at ILVO was conducted under reduced N fertilization (-50 units of nitrogen compared to normal fertilization based on advice). These trials, conducted over three years at three locations, have shown that varieties with a high yield potential decrease proportionally more in yield compared to varieties with a lower yield potential. The differences were small in terms of quality and dry matter content.

Organic farming, including for maize, is increasing. Based on the variety research, five years of silage maize trials were set up on organic farms, with varieties that are first grown under conventional methods then propagated via an organic protocol.

In addition to yield and quality determination, specific characteristics that are important for organic farming (early growth and rate of soil cover; N-efficiency) were assessed. The purpose of these trials is to establish specific criteria for variety acceptance and later a list of recommended varieties for organic cultivation. The data were processed in a separate publication.

Since 1 January 2004, organic growers have been required to use seeds for their cultivation that have been propagated according to an organic protocol. The range of organically propagated varieties is displayed at www.organicxseeds.com. In the future it will also be important to provide information about the value for cultivation and use of these varieties under Belgian operating conditions.