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Spotlight
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oil health, which can be defined as
the ability of the soil to function as a
vital, living ecosystem that sustains
plants, animals and humans, is
closely linked to soil organic matter. It takes
time for conservation agriculture (CA) prin-
ciples implemented in a cash grain crops
rotation to impact positively on soil health.
In some cases soil health can even stagnate.
In this article the following CA aspects un-
der investigation at the cover crop screen-
ing trial on the farm Humanskraal, Ottosdal
area, will be discussed: Maize grain yields,
water use efficiency, soil organic matter
and the role it fulfils in regenerating the soil
with the co-operation of microorganisms.
An integrated livestock-cover crop system
as part of a cash crop rotation as a possible
vehicle to speed up the improvement of soil
health, is also scrutinised. Regenerating the
soil in the transitional phase of CA should be
prioritised. The message of ‘restore before
you conserve’ should be loud and clear.
Grain yield and water
use efficiency
Maize grain yields under normal circum-
stances are closely correlated with rainfall.
The average rainfall for the Ottosdal region
in the long-term is just above 500mm. Study-
ing
Graph 1
, it is clear that in the past five
years there were no normal rainfall patterns.
For maize to produce grain, a minimum rain-
fall of 230 mm rain during the growing peri-
od is necessary to produce enough biomass
to support grain yield.
After sampling the maize total biomass
and determining the dry matter percentage
(DM%) for all treatments in the screening
trial, maize grain was calculated by dividing
the dry matter yield by two. This was done
based on the theory that maize has a har-
vesting index of 50%. Water use efficiency
was calculated by dividing the estimated
grain yield of the different treatments by the
total effective rainfall for 2017.
Maize yields were exceptionally high in ro-
tation with 16 cover crops and as a mono-
culture maize treatment. On average maize
November 2018
40
GERRIE TRYTSMAN,
independent researcher and
GEORGE STEYN,
Humanskraal farm, Ottosdal
CA
Enhancing soil
health through livestock
integration in transitional phase
Graph 1: Monthly rainfall (Oct - May) at Humanskraal from 2013.
1: A growth stage of maize in which leave samples were taken.
1