Agriculture Reference
In-Depth Information
compared with 65 days ha −1 in the CT method (Ngwira et al. 2012). The return labor
was double in the CA system as compared with the CT system, and the return per
hectare in the CA system was 61% higher than in CT.
CA increases labor demand in relation to weeding, as there is no mechanical
disturbance of the weeds. Herbicides have therefore been introduced in Zambia
and Malawi as part of the promotion of CA. However, in the 2009-2010 season in
Zambia, still only 8% of the farmers in a survey of 429 farmers used herbicides;
however, the number is increasing year by year (Nyanga et al. 2011). Glyphosate was
the herbicide most frequently used, but many farmers did not use the herbicide cor-
rectly (Umar et al. 2011). The concentration of the herbicide was often too low and
the water used is often inappropriate (dirty).
Experimental research on CA may not always give a good estimate of the yield
effect under real farming conditions. One important factor affecting yield is the sow-
ing time. Sowing is often delayed in Zambia and Ethiopia when plowing is practiced
because there are not enough oxen available to plow the land on time (Aune et al.
2001). The average sowing time for the different tillage methods was November 9,
12, 12, and 23 for farmers practicing basins, hand hoeing, ripping, and plowing,
respectively (Umar et al. 2012). Changing from plowing to ripping can therefore
allow farmers to sow earlier because of the lower labor demand in ripping as com-
pared with plowing. The labor demand of the plowing operation was found to be 3.8
person-days ha −1 , while the ripping operation was 0.8 person-days ha −1 . The CFU
in Zambia has been encouraging farmers to prepare the basins in the dry season to
allow them to sow early in the rainy season. However, farmers have generally not
taken up this practice as they find it very difficult to till a dry soil and they seem to
emphasize other activities in the dry season.
10.2.3 E ffECt of CA on s oil P roPErtiEs And W AtEr A vAilAbilitY
The effect of CA on soil properties is dependent on which tillage method is used,
additions of organic matter to the systems, and the type of crop rotation practiced.
In Zambia, it was found that CA without recycling of residues did not have
any effect on soil chemical properties (Umar et al. 2011). In Burkina Faso and
Zimbabwe, it has been found that the soils in the planting basins (zai) have
increased soil carbon and nitrogen, and a lowered C/N ratio as compared with the
soil between the basins (Sawadogo 2011; Mupangwa et al. 2013). Direct sowing
and residue retention have been found to increase soil organic matter content in
Zimbabwe (Thierfelder and Wall 2012). The increase in soil organic carbon was
higher on a clay soil than on a sandy soil. From Ethiopia, it has been shown that use
of permanent ridges and retention of crop residues can significantly increase soil
organic matter content and reduce erosion and runoff as compared with a system
with CT (Araya et al. 2012).
In Malawi, it was shown in a long-term experiment that the main reason for the
yield-increasing effect of zero tillage and mulching is the increase in infiltration by
24%-40% as compared with the CT system in the country (Thierfelder et al. 2013).
Results from Zimbabwe showed that zero tillage with residue retention had higher
infiltration rates than plowing without residue retention (Thierfelder and Wall 2012).
Search WWH ::




Custom Search