Agriculture Reference
In-Depth Information
practiced. Few studies have examined the effect of a full CA package on yield. Often,
only one element of CA is studied, such as the effect of tillage or the mulch effect.
A survey of 129 farmers that have been involved in a project on CA in Zambia
showed yield levels of 1.8, 5.2, 2.3, and 3.8 tons ha
−1
for hand hoeing, planting basins,
ripping, and plowing, respectively (Umar et al. 2011). On-station experiments by the
Golden Valley Agricultural Research Trust in Zambia have shown yield levels of 4.0,
6.3, 5.3, and 5.5 tons ha
−1
for hoe tillage, basin tillage, ripping, and plowing, respec-
tively (Umar et al. 2011). This shows that the yield level in basins is consistently
higher than in other tillage systems in Zambia. The yield-increasing effect of the
basins has been particularly apparent in the dry years. The reason why basins have
been found to increase yields is probably related to increased water infiltration in the
basins and the better nutrient use efficiency, as the fertilizer is also placed adjacent to
the seeds in the basins. In years with excessive rainfall, problems with waterlogging
in the basins were observed in Zambia (Umar et al. 2011). The reasons why farmers
in Zambia find it difficult to adopt CA is related to lack of labor (38%), lack of land
(30%), and no timely access to input (9%) (Umar et al. 2012). In Tanzania, no yield
difference was found between ripping and basins; however, these CA tillage meth-
ods increased yields by 50% as compared with plowing (Rockström et al. 2009). In
Zimbabwe, contrasting results have been found on the use of basins. The average
yields from 15 regions across Zimbabwe showed an increase from 970 kg ha
-1
for non-
CA farmers to 1546 kg ha
-1
for CA farmers practicing basins (Marongwe et al. 2011).
However, a 4-year study (one site) in Zimbabwe was not able to find any significant
difference in maize grain yield between plowing, ripping, and basins (Mupangwa et
al. 2013). In Burkina Faso, it has been found that planting basins (zais) can, under
certain conditions, double and quadruple yields (Sawadogo 2011). These results show
that planting basins will, under most conditions, increase yield.
In Malawi, it has been found that CA can also increase yield as compared with
conventional tillage (CT) (Ngwira et al. 2012). The CA system (direct planting, straw
mulch, and herbicide application) increased yield compared with CT (ridge splitting,
without mulch, and manual weeding) by 41%. The yield benefits of CA in Malawi
have been found to be higher in drylands at low altitudes than in higher altitudes with
better rainfall (Thierfelder et al. 2013). There was also considerably less risk associ-
ated with CA in areas with low rainfall (Ngwira et al. 2013). Multilocational (nine
sites) and long-term studies (up to 8 years) in Malawi comparing zero tillage and
retention of crop residues (CA) with ridge splitting and burrowing of crop residues
(CT) showed that in the initial years, there were no clear yield benefits of the CA sys-
tem, but after 5 years CA gave clearly higher yields than CT (Thierfelder et al. 2013).
Although the yield benefit is not apparent in the initial years, it may still make sense
for the farmers to practice CA because of the labor-saving effect. In Zimbabwe, it has
been shown, as in Malawi, that CA gives no initial yield benefit over CT; however, the
yield in CA increases over time as compared with CT (Thierfelder and Wall 2012).
In Tigray, Ethiopia, no yield difference was found between reduced tillage (one
pass with the maresha) and CT (four passes with the maresha) (Habtegebrial et al.
2007). Studies in central Ethiopia on nitosols also confirmed that reduced tillage
can produce equal yields as CT (Tulema et al. 2008). However, reduced tillage plots
had more weed infestation than plots under CT. Zero tillage for teff was found to
