SA Graan Februarie 2015

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February 2015
ON FARM LEVEL Conservation agriculture
If N is to be applied, it will be to promote microbial activity and will
also prevent the decomposing plant material from tying up nitrogen
needed by the following crop. This way it can be reincorporated
prior to establishing the succeeding crop. If the oats is to be used
for cattle production, it can either be grazed with sufficient periods
of rest for regrowth, or hay and/or silage can be made.
Soil conservation and health benefits
Common oats has proven to be an effective method to control
weeds, thereby reducing the need for chemical weed control. Oats
has the characteristics of germinating very quickly and to beat the
weed species growing in the same area.
In addition to this, oats releases an allelopathic compound (plant-
made chemicals) that hinders the germination and growth of weeds
for several weeks. These compounds can however also hinder
the growth of subsequent crops, such as wheat, peas, lettuce and
rice and therefore this trait should be kept in mind when planning
the timing and sequence of a crop-rotation programme for a farm.
These allelopathic compounds tend to break down in about three
weeks; nevertheless, consult a specialist for more detail regarding
specific crops.
Literature has shown that common oats produces about 5 tons/ha
of dry matter and takes up about 7,25 kg of N in each ton of dry
matter. The tissue N content of oats is about 1,2%. As previously
stated, the addition of N fertiliser will promote microbial activity
and will also prevent the decomposing plant material from tying up
nitrogen needed by the following crop.
Alternatively, a mixed cover crop stand of oats and a legume can
minimise potential problems of N immobilisation after cover crop
is incorporated. To allow time for residue decomposition, allow two
to three weeks after cover crop incorporation before planting the
succeeding crop.
Incorporating oats into the soil also improves the soil “health” by im-
proving the soil structure which improves water infiltration. Most of
this soil improvement will occur in the top soil layer. As the residues
decompose, the organic matter additions provide food for the grow-
ing microbial population.
When planted at low seeding rates, oats can also be used as a nurse
crop for establishing slower growing legume cover crops. If the oats
grows too vigorously, it can be cut to allow better growth of the leg-
ume intercrop.
Management challenges
With oats being able to suppress weed growth, the allelopathic
compounds that provide oats with this attribute may stunt the
growth of subsequent cash crops. Allow three weeks for the allelo-
pathic compounds to decompose.
When oats is grown for grain or forage, it can have more insect
problems (such as wireworms, cutworms, armyworms, aphids and
mites, thrips, leafhoppers and grubs). Cultivars resistant to rust and
blight have been developed.
Animal production aspects
Other than the soil improvement benefits of oats, this small grain
crop is also commonly used as forage for animal production sys-
tems. Oats is relatively competitive with most annual winter forage
crops and can be grazed when 20 cm tall.
Grazing should be managed to remove the forage before be-
coming too stemmy. Oat hay makes a satisfactory hay crop if cut
when the stems and leaves are still green. Oats make the most nu-
tritious hay when cut in the soft dough stage because of the higher
protein content.
Oats used for forage has a greater tendency than wheat or barley
to accumulate potentially toxic levels of nitrate in plant forage un-
der conditions of drought, hail damage, or other growth factors that
cause cessation of normal growth patterns. Under such conditions,
a laboratory diagnosis of oats forage for nitrates would give helpful
information relative to its safety.
Oats can be regarded a good “growing” feed for cattle but of having
a lesser value than maize, grain sorghum or wheat when used as
the major energy source in finishing rations. Rations containing very
high levels of oats or even rations with no roughage do not produce
comparable weight gains to those of maize and sorghum.
Oats may have a place in all-concentrate diets as a supplement for
cereals which have low fibre contents. It is however still a concen-
trate feed. Death can occur from acidosis due to overconsumption of
oat grain by young animals. As with all other concentrates, sudden
excess consumption must be avoided.
Conclusion
There is no doubt that oats is an excellent crop to tolerate low
fertility soils, for suppressing weeds due to its rapid growth rate and
establishment as a “catch crop” for taking up and storing excess N.
With its vigorous root system it also provides for good erosion con-
trol by increasing soil organic matter content to improve soil struc-
ture. Other than all the soil improvement benefits it has, it can be
used for animal grazing systems and for providing lasting residues
for succeeding crops.
For more information, contact Dr Wayne Truter at wayne.truter@
up.ac.za, Prof Chris Dannhauser at
Dr Hendrik Smith at or Mr Gerrie
Trytsman at
CONSERVATION AGRICULTURE