24
and as an approach to reverse soil degradation (Lal 2015). Crop establishment
methods under CA include direct sowing using planters (mechanised), planting
with the use of a dibble stick (manual), ripping of the soil followed by sowing
(mechanised) and the use of permanent planting basins (manual). The use of permanent raised beds (mechanised) is a method employed on heavy soil prone to waterlogging. CA has been proposed as an approach to increase yields, for carbon
sequestration, to enhance biodiversity and to save on labour and costs (FAO 2018).
Access to appropriate farm machinery is a key factor for upscaling of CA across the
continents (Lal 2015).
2 Conservation Agriculture in Africa
CA is progressing in Africa at a pace of around 150,000 hectares (ha) per year, and
the area under CA has tripled during the last 10 years reaching around 1.5 million
ha (Kassam et al. 2018). This represents about 1% of the farmland in Africa. South
Africa is the African country with the most land farmed using CA methods (mechanised CA). Despite this progress, many at the 2nd African Congress on Conservation
Agriculture in 2018 were concerned about the slow uptake of CA in Africa. Only
limited research has been conducted on CA by the national research institutions,
with most of the research being undertaken by international research centres such as
CIMMYT.
1
The knowledge base on CA in Africa has increased rapidly during the last
10 years with regard to yield response, environmental impact and factors determining adoption. A meta-study including 42 studies from Africa showed that zero tillage (ZT) has a slightly lower yield (−24 kg ha
−1
) than conventional tillage (CT), but
zero tillage (ZT) with mulch compared to conventional tillage gave an average yield
increase of 294 kg ha
−1
in the first 3 years, whilst this yield increase was 487 kg ha
−1
when ZT with mulch was practised for more than 3 years (Corbeels et al. 2014).
A meta-study across the Earth’s semi-arid and sub-humid conditions also showed
that ZT without mulching gave a lower yield than CT (Rusinamhodzi et al. 2011),
and mulching improved yield over time. This shows that mulching is a key factor in
the success of CA. There are contradictory results regarding the most suitable rainfall conditions for CA. Corbeels et al. (2014) showed that CA gave higher yields
than conventional tillage when rainfall was above 1000 mm compared to below
600 mm, whilst Rusinamhodzi et al. (2011) showed the opposite effect. CA has
been found to perform better on loamy soil compared to sandy or clay soil (Corbeels
et al. 2014). The reason is probably that CA will not work well where there are
problems with waterlogging or in dry areas where it is difficult to produce sufficient
quantities of mulch. Lal (2015) has proposed to develop a soil suitability guide to
1 International Maize and Wheat Improvement Center.
J. B. Aune
and as an approach to reverse soil degradation (Lal 2015). Crop establishment
methods under CA include direct sowing using planters (mechanised), planting
with the use of a dibble stick (manual), ripping of the soil followed by sowing
(mechanised) and the use of permanent planting basins (manual). The use of permanent raised beds (mechanised) is a method employed on heavy soil prone to waterlogging. CA has been proposed as an approach to increase yields, for carbon
sequestration, to enhance biodiversity and to save on labour and costs (FAO 2018).
Access to appropriate farm machinery is a key factor for upscaling of CA across the
continents (Lal 2015).
2 Conservation Agriculture in Africa
CA is progressing in Africa at a pace of around 150,000 hectares (ha) per year, and
the area under CA has tripled during the last 10 years reaching around 1.5 million
ha (Kassam et al. 2018). This represents about 1% of the farmland in Africa. South
Africa is the African country with the most land farmed using CA methods (mechanised CA). Despite this progress, many at the 2nd African Congress on Conservation
Agriculture in 2018 were concerned about the slow uptake of CA in Africa. Only
limited research has been conducted on CA by the national research institutions,
with most of the research being undertaken by international research centres such as
CIMMYT.
1
The knowledge base on CA in Africa has increased rapidly during the last
10 years with regard to yield response, environmental impact and factors determining adoption. A meta-study including 42 studies from Africa showed that zero tillage (ZT) has a slightly lower yield (−24 kg ha
−1
) than conventional tillage (CT), but
zero tillage (ZT) with mulch compared to conventional tillage gave an average yield
increase of 294 kg ha
−1
in the first 3 years, whilst this yield increase was 487 kg ha
−1
when ZT with mulch was practised for more than 3 years (Corbeels et al. 2014).
A meta-study across the Earth’s semi-arid and sub-humid conditions also showed
that ZT without mulching gave a lower yield than CT (Rusinamhodzi et al. 2011),
and mulching improved yield over time. This shows that mulching is a key factor in
the success of CA. There are contradictory results regarding the most suitable rainfall conditions for CA. Corbeels et al. (2014) showed that CA gave higher yields
than conventional tillage when rainfall was above 1000 mm compared to below
600 mm, whilst Rusinamhodzi et al. (2011) showed the opposite effect. CA has
been found to perform better on loamy soil compared to sandy or clay soil (Corbeels
et al. 2014). The reason is probably that CA will not work well where there are
problems with waterlogging or in dry areas where it is difficult to produce sufficient
quantities of mulch. Lal (2015) has proposed to develop a soil suitability guide to
1 International Maize and Wheat Improvement Center.
J. B. Aune