Photo 1: Soil with surface crusts and signs
of severe erosion
At the stage when the cover crop was fully
developed, photo 2 was taken on the 14
April 2016; the crop yielded an average
biomass production of 12t DM/ha. Photo 2: Fully developed mixed summer
cover crop system
in on-going research in Grain SA’s on-farm CA
trials across the country. The establishment
of perennial pastures is another possible
solution, as part of the crop diversity within
integrated crop-livestock systems, to facilitate
the restoration process.
From a degraded soil to commercial maize
production colonization of mycorrhizal fungi. It has been
shown in the past that only 20% P fertiliser is
taken up during the first year after application,
while soil microbes provide plants with the
amounts of nutrients required.
12 kg of K/ha - since there is sufficient
amounts of K in the soil, this application was
just to establish strong vigorous seedlings;
additional Sulphur and Zinc were also applied.
No further inputs as far as soil fertility
management were deemed necessary. This
was due to a great supply of nutrients in the
cover crop residues that will be made available
as the CC biomass decomposes through
microbial activity.
In order to put this field back into maize
production (as was aimed for), the following
fertilizer application rates (side dress) was
used to establish the maize crop aiming for a 5
t/ha yield in the 2016/2017 season:
33 kg of N/ha – this amount of N will cover a
yield target of only 2 ton/ha; the remaining
N required will be provided through nutrient
cycling and C decomposition of the CC mix’s
DM and roots. Depending on the production
of the CC, a saving of 70-80 kg/ha of N can
quite easily be attained during the first year
(see Table 1, Part 1).
18 kg of P/ha – this amount of P will cover a
yield target of 5 ton/ha; from the Haney soil
analysis it is clear that C content and microbial
biomass activity is not yet sufficiently restored
to recycle and/or release sufficient soil P to
support plant P requirements for a yield target
of 5 ton/ha. It is expected that more P will
be released from the soil in the next couple
of years through biological processes and
AgriKultuur |AgriCulture
Photo 1 shows the soil surface before cover
crops was planted. Low levels of cover with
a soil surface crust and erosion can be seen.
The photo was taken on 27 January 2016, just
before the cover crops were planted.
Photo 3 shows the CC residues (left standing)
killed by the winter frost, taken on 2
September 2016. A decision was made not
to flatten it because of the positive effect the
standing residues would have had on wind
and water erosion. The cooler soil under the
residue cover will also benefit the water cycle
due to the lower evaporation from the soil
surface.
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