Why undersow maize crops?

Maize undersown crops offer a multitude of benefits, particularly for the soil fertility. Planting silage maize results in a strongly negative humus balance. This can be partly compensated for through the use of undersown crops. Already 200 kg/ha humus is produced by sowing 15 kg of undersow. At the same time, humus formation in the soil takes place through the huge root mass of the grasses. The good root penetration of the soil promotes the biological activity of the microbes and earthworms, thereby increasing the aggregate stability of the soil. Particularly, the high proportion of fine roots, e.g. Landsberger Mix, ensures good structural stability. The carrying capacity of the soil is improved, which the farmer benefits from predominantly through the maize yield (Video: Maize undersowing keeps the soil stable). Furthermore, the intensive root penetration of the soil leads to improved tilth when sowing the following crop.

Organic farming trials confirm 20-80 % suppression of weeds by undersown crops. Additionally, the undersown crop removes excess nitrogen from the soil, thereby preventing it from being leached and making it available to the following crop. The undersown crop can take up the excess nitrogen, which is mineralised in the soil and converted to biomass, even if the maize has already reached its N-requirement. This helps to maintain the Water Framework Directive and lowers nitrate release into the ground water. For this reason, the undersown crops should be used especially in regions with soils at risk from leaching. Furthermore, it is possible to apply slurry or biogas substrates to the area with undersown crops after the maize harvest.

There are currently various possible sowing procedures that can be used at different time points and with different mixtures. The aim of the individual mixtures is not to weaken the competitiveness of the maize at the respective sowing times. Thus, early undersown crop mixtures can already be applied shortly before or after the seed using a conventional drill or grass drill. The later mixtures can be applied with the aid of a pneumatic spreader or even with the slurry tanker. To do this, the grass seeds are introduced using a hose attached to the intake sack at the same time as the slurry is fed into the tanker.

 

Ideally, the aim should be to split herbicide treatments for crop protection. By doing so, it is possible to perform a treatment with a soil active ingredient relatively early at the 2-3 leaf stage, and then a second treatment at the 5-6 leaf stage. Here, specific herbicides that work via the foliage can then be selected according to the type of weed. A number of the current substances are generally compatible with undersown crops and can be applied in a targeted manner to eliminate problem weeds such as sorghum. However, care should be taken that the undersown crop is sown at least two weeks after the first herbicide treatment so that the soil-applied herbicide does not cause severe damage to the young seedlings. You can request precise herbicide recommendations from the Chamber of Agriculture and your local DSV advisor.

 

A deciding factor for the success of the undersown crop is the adapted maize plant protection. Meanwhile there are a number of strategies available which make weed control possible. There are numerous herbicides (see table) that are compatible with undersown crops. However, a period of two weeks should be allowed after each spraying before sowing the grasses. A crop protection strategy is even possible against problem weeds like sorghum. At very high weed pressure, the undersown crop is however only possible with compromises in the herbicide effect. Your consultant can provide you with the current recommendations.

In addition to the use of undersown crops as green manure, they also offer an interesting source of feed for dairy farms and biogas plants. Under good conditions, a further cut can be made in the following spring after the undersown crop. In particular, the mixtures Humus-Plus-ENERGIE and Landsberger Mix form high biomass growth after the maize harvest, which can be harvested during the next spring. A proliferation in the grass seed is a further economic benefit of the undersown crop. But even if not used, 15 kg seed/ha provide plenty:
N-binding, ground greening, better navigability, improved humus balance and nutrient storage:
little effort – huge effect.
For an effective control of the corn borer, you should intensively shred the maize stubbles with mulchers after the harvest. Through this method, the tillering of the undersown grasses is stimulated and therefore the sward density increases.