31
farming practices. One such traditional tillage system is the Derdero method, which
consists of broadcasting the seed after repeated tillage followed by one pass with the
maresha to make ridges or narrow raised beds (Nyssen et al. 2011). Most of the
seeds will therefore germinate on the ridge or raised bed, making the plants less
exposed to waterlogging. The distance between the furrows is about 60 cm. In the
following years, only one pass with the maresha is made to bury the seeds and
rebuild the ridge, thus representing a minimum tillage system. An improvement of
the system has been developed using the application of glyphosate to control weeds
and retaining 50% of the standing straw for use as mulch. The retained straw should
not be grazed. A major advantage is a reduced need for traction power, as only one
pass with the maresha is practised in the years following the establishment of the
ridge/raised bed. Results from Tigray show that it took at least 3 years before there
was a yield benefit using the Derdero tillage method compared to conventional tillage (Areya et al. 2016). The soil properties such as organic carbon, total N, available
P and soil microbial biomass, infiltration rate and aggregate stability improved as a
result of the raised bed.
5 Effect of CA on Labour Use and Economic Return
Reduced tillage can decrease labour demand if minimum tillage is combined with
the use of herbicides. Total labour use in maize production in the South Achefer
region (northwestern Ethiopia) was reduced from 79 hours (h) ha
−1
in conventional
tillage to 57 h ha
−1
using minimum tillage with herbicides, and oxen hours were
reduced from 17 h ha
−1
with traditional tillage to 5 h ha
−1
with minimum tillage
(Jaleta et al. 2016). However, in an experiment in maize (in the Rift Valley) where
herbicides were not used, labour use for land preparation and weeding was 37, 41
and 51 h ha
−1
for conventional tillage, reduced tillage and zero tillage, respectively
(Sime et al. 2015). Labour use for tillage was less in zero tillage and reduced tillage
but higher weeding compared to conventional tillage. This higher labour use combined with lower yield resulted in a lower gross margin for reduced tillage and zero
tillage compared to conventional tillage (Sime et al. 2015). The gross margin in zero
tillage was 52% less than in conventional tillage and 22% less in reduced tillage
compared to conventional tillage. Mulching in zero tillage plots compared to nonmulch ZT plots increased gross margin with 74% as a result of higher yields and
less labour use for weeding (Sime et al. 2015).
Field experiments with teff show that reduced tillage gives a satisfactory economic return on Vertisol (Tulema et al. 2008). This study showed that reduced tillage gave an equal gross margin to conventional tillage on a Vertisol, whilst on a
Nitisol, conventional tillage gave a 47% higher gross margin than reduced tillage.
Experiments conducted on Vertisols in Tigray also confirm that reduced tillage gives
yields as high as conventional tillage (Habtegebrial et al. 2007), with the only difference being that there is more weed infestation in reduced tillage plots. Experiences
of Sasakawa Global 2000 also showed that reduced tillage with mulching and
The Prospects for Conservation Agriculture in Ethiopia
farming practices. One such traditional tillage system is the Derdero method, which
consists of broadcasting the seed after repeated tillage followed by one pass with the
maresha to make ridges or narrow raised beds (Nyssen et al. 2011). Most of the
seeds will therefore germinate on the ridge or raised bed, making the plants less
exposed to waterlogging. The distance between the furrows is about 60 cm. In the
following years, only one pass with the maresha is made to bury the seeds and
rebuild the ridge, thus representing a minimum tillage system. An improvement of
the system has been developed using the application of glyphosate to control weeds
and retaining 50% of the standing straw for use as mulch. The retained straw should
not be grazed. A major advantage is a reduced need for traction power, as only one
pass with the maresha is practised in the years following the establishment of the
ridge/raised bed. Results from Tigray show that it took at least 3 years before there
was a yield benefit using the Derdero tillage method compared to conventional tillage (Areya et al. 2016). The soil properties such as organic carbon, total N, available
P and soil microbial biomass, infiltration rate and aggregate stability improved as a
result of the raised bed.
5 Effect of CA on Labour Use and Economic Return
Reduced tillage can decrease labour demand if minimum tillage is combined with
the use of herbicides. Total labour use in maize production in the South Achefer
region (northwestern Ethiopia) was reduced from 79 hours (h) ha
−1
in conventional
tillage to 57 h ha
−1
using minimum tillage with herbicides, and oxen hours were
reduced from 17 h ha
−1
with traditional tillage to 5 h ha
−1
with minimum tillage
(Jaleta et al. 2016). However, in an experiment in maize (in the Rift Valley) where
herbicides were not used, labour use for land preparation and weeding was 37, 41
and 51 h ha
−1
for conventional tillage, reduced tillage and zero tillage, respectively
(Sime et al. 2015). Labour use for tillage was less in zero tillage and reduced tillage
but higher weeding compared to conventional tillage. This higher labour use combined with lower yield resulted in a lower gross margin for reduced tillage and zero
tillage compared to conventional tillage (Sime et al. 2015). The gross margin in zero
tillage was 52% less than in conventional tillage and 22% less in reduced tillage
compared to conventional tillage. Mulching in zero tillage plots compared to nonmulch ZT plots increased gross margin with 74% as a result of higher yields and
less labour use for weeding (Sime et al. 2015).
Field experiments with teff show that reduced tillage gives a satisfactory economic return on Vertisol (Tulema et al. 2008). This study showed that reduced tillage gave an equal gross margin to conventional tillage on a Vertisol, whilst on a
Nitisol, conventional tillage gave a 47% higher gross margin than reduced tillage.
Experiments conducted on Vertisols in Tigray also confirm that reduced tillage gives
yields as high as conventional tillage (Habtegebrial et al. 2007), with the only difference being that there is more weed infestation in reduced tillage plots. Experiences
of Sasakawa Global 2000 also showed that reduced tillage with mulching and
The Prospects for Conservation Agriculture in Ethiopia