Maize cultivation can lead to problems in some locations despite specialist production
techniques. The problems include erosion during the maize seedling development as well as nitrogen
discharge and soil compaction after the harvest. Here, undersown crops repair the situation and
bring additional benefits that are financially worthwhile. For example, there are federal states in
which undersown crops are subsidised (e.g. Lower Saxony). Furthermore, maize undersown crops can
help to achieve the target of the Erosionsschutzkataster (Erosion Protection Land Registry), the
humus balance and the reduction in nitrogen discharge into the water protection areas.
But beside the direct requirements demanded, for example due to erosion protection for the
planting of undersown crops, many farmers would also not like to do away anymore with sowing of
Undersown crops delight the farmer and the earthworms
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.
Weed suppression and active groundwater protection are included for free
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.
✔ Nutrient storage and protection against leaching
✔ Increased biological activity
✔ Adherence to the requirements of Cross Compliance
✔ (Humus) in short crop rotations
✔ Erosion protection
✔ Breaking up of short maize rotations
✔ Immediate soil coverage after harvest
✔ Possible use of the growth as substrate in spring
The following points must be observed for successful establishment of an undersown crop
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.
Strategies for using crop protection:
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.
Development of the undersown crop (0 = poor, 9 = very good)
Motivell forte + Peak + B 235
Calisto/Calaris (0,7) + B 235 / + Cato
Motivell forte + Peak + B 235 + Calaris (0,7)
Clio Star + Spectrum
Lodin / Mais Banvel WG / Harmony SX
Source: LWK NRW, 2014
Undersown crops sown with the maize seeds require a different strategy. As they are already
established, a certain weakening of the crop as a result of the herbicide is absolutely desirable.
This thereby counteracts possible overgrowth and existing competition with the young maize. This
strategy is possible with post-emergence herbicides: Laudis 2.0 l/ha + B 235 0.2 l/ha or Laudis 1.5
l/ha + Callisto 0.3 l/ha + B 235 0.2 l/ha (Source: LWK NRW, 2014).
Using the undersown crop
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.