Photo 3: A 100% cover by the mixed
summer cover crop residues Photo 4: Field with summer cover crop
residues just before planting the maize
crop
Photo 4 was taken just before the maize was
planted on 12 December 2016; note that the
easy decomposable leaves containing the
most nutrients were already decomposed
by the microorganism. Only the woody
plant material containing the less digestible
tannins and lignin fragments in the residues
were left. It is in decay or decomposition
that this organic matter becomes useful as it
becomes the fuel for ‘bacterial fires’ in the soil,
which operates as a factory producing plant
nutrients. Photo 5 shows the maize crop at tasselling
and silking stage with no signs of any nutrient
deficiencies. The lower older leaves remain
green. By April 2017 the predicted maize
yield on this field was 7.5 ton/ha, indicating
by all standards to a successful regeneration
(restoration) of a degraded soil into full maize
production using the principles of CA and
ISFM. A good tool to monitor soil fertility or the
uptake of plant nutrients is leave analysis (at
this growth stage); plant nutrient levels should
match the values shown in Table 4.
Table 4: Critical plant nutrient levels in maize leaves
Critical plant nutrients levels in leaf opposite and below the ear at tasselling
% of DM
Ppm of
DM
N P K Mg Ca S Zn Fe Mn B
2.9 0.25 1.9 0.15 0.4 0.15 15 25 15 10
Source: Hoeft & Peck,
1991
Conclusion
This case study has demonstrated that
CA facilitates the successful application of
ISFM, the recovery of critical soil ecosystem
functions and the restoration of degraded
soils. This process requires from producers
a quality implementation and adaptation of
AgriKultuur |AgriCulture
CA practices such as crop diversity and more
specifically, multi-specie cover crop systems. It
also requires an understanding of soil health
and a long-term vision on soil restoration or
regeneration, especially under dry and sandy
soil conditions.
17