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Januarie 2018
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CA proofs to be key in
sustainability of grain systems
A
number of producers in the Vrede
area are participating in a Grain SA
Conservation Agriculture Farmer
Innovation Programme (FIP) re-
search project, which is funded by the
Maize Trust. This article will put the spotlight
on the farm Skulpspruit of Mr Izak Dreyer
where CA has been done for five years.
Some experiments with winter cover crops
were done in strip plots during the winter
of 2015 and the results of the following
maize crops were shared in the March 2017
edition of
SA Graan/Grain
. Those results
were so convincingly positive, even for a
year when extremely dry conditions pre-
vailed for most of the summer, that Dreyer
immediately stopped experimenting and
started implementing cover crops on a
much bigger scale.
Mixed winter cover crop systems were
subsequently planted after his soybean.
Livestock was then used to utilise the
cover crops during the winter months to
produce beef to the net margin of roughly
R3 000 (2016) to R7500 (2017) per hectare.
This article will report on the most recent
findings since winter cover crops and live-
stock were integrated into the farming sys-
tem in 2016.
CA and rainfall use
efficiency
Graph 1
shows how various treatments in-
fluenced the water content of soils. The pre-
summer rain observations were made three
weeks before the rainy season commenced.
It can therefore be assumed that the treat-
ments with no-till winter cover crops almost
completely dried out the soil prior to the
first rains.
Cover crops treatments were almost as dry
as the tillage treatment. The no-till soybean
control treatments were significantly wet-
ter than the cover crop treatments. Soil wa-
ter content during September and most of
October 2016 was lower than the compara-
ble levels measured the previous year be-
cause of below-average rainfall.
The control treatments where maize was
grown the previous year had generally drier
soils than the soybean fields. This would be
expected since maize grows well into au-
tumn as opposed to soybeans that are har-
vested early (end of March) allowing more
soil moisture conservation.
Graph 1 indicates that soil moisture conser-
vation through winter fallow systems (com-
pared to full utilisation with winter cover
crops, i.e. a green fallow system) was not
essential. The first summer rains fell over
a period of three days during the latter half
of October totalling almost 70 mm, which is
almost equal to the long-term average for
October. Graph 1 also shows that this first
rain wetted all treatments properly (effec-
tive soil depth is 60 cm).
All differences were quickly removed even
before planting started and maize yields
would obviously not be affected by different
soil water contents. Yields varied around
8 t/ha, which were comparable to yields in
the previous year. The only difference this
year was that any soil water differences
caused by cover crops were wiped out even
before planting commenced.
It took until the last week of January the pre-
vious year before rain showers increased to
levels that were sufficient to eliminate soil
water differences.
It was previously shown that water infiltra-
tion rate improved on the no-till fields and
it increased even more where winter cover
crops were planted. Those results and ex-
cellent yields indicated that there were no
soil compaction problems. Nevertheless,
more soil compaction studies were done to
improve producers’ and scientists’ under-
standing of this topic.
ON FARM LEVEL
Conservation agriculture
DR ROBERT STEYNBERG,
senior agronomist, VKB and
DR HENDRIK SMITH,
CA facilitator, Grain SA
1a and 1b: A concentration of roots was observed directly
beneath the plant row (1a) and a second concentration was
observed midway between rows where a winter cover crop
row was previously situated (1b).
1a
1b
Farmer innovation programme