Agriculture Reference
In-Depth Information
al. 2003). Furthermore, CA technologies together with the application of organic
and inorganic fertilizers, maize stover combined with inorganic fertilizers, and crop
rotations and intercropping have resulted in yield gains over the farmers' practice in
most farming systems in the region. However, experiences show that although the CA
technologies discussed in this chapter have shown promising results, most of them
remained limited to participating farmers within the small project sites. Therefore,
there is a need for further research aimed at assessing, improving, and upscaling the
potential contribution of CA practices to sustainable smallholder agriculture, par-
ticularly in semiarid areas of East Africa in the context of climate change, soil res-
toration, gender equity, and agricultural productivity. It is apparent from this chapter
that CA has increased the yield of most crops particularly in the fragile ecosystems.
It can be concluded that CA for crop production is the best model that can be used to
promote small-scale farming on fragile ecosystems in East Africa.
12.1.1 B
ackground
East African countries depend largely on agriculture. However, land degradation and
soil fertility depletion remain major biophysical constraints to agricultural productivity,
partly attributable to limited investment in soil-improving technologies, lack of appropri-
ate information, and low adoption of available technologies owing to inadequate incen-
tives. Nutrient mining, which is rampant in many smallholder farms of East Africa, is
exacerbated by continuous cropping; inadequate nutrient replenishment in relation to
plant demand; and high rates of soil erosion, leaching, and removal of crop residues from
the fields (Lal 2001; Lynam et al. 1998). As a result, soil fertility has continued to decline
to levels that are currently prohibitive to profitable agriculture. According to the Food
and Agriculture Organization of the United Nations (FAO) Global Land Degradation
Assessment, almost a quarter of the global land area was degraded between 1981 and
2003, with one of the most severely affected areas being Africa south of the equator
(FAO 2006a). Major nutrients such as N, P, and K balances for 13 countries in sub-
Saharan Africa show negative trends with about 200 million ha of cropland having lost
660 kg N/ha, 75 kg P/ha, and 450 kg K/ha in the last 30 years, and with high to very
high depletion rates in East Africa (Cobo et al. 2010). As a result, the originally fertile
lands that yielded 2-4 t/ha of cereal grains have been degraded, with cereal crop yields
of <1 t/ha becoming common (Sanchez 2002). The new “Vision for African Agricultural
Research” developed by Forum for Agricultural Research in Africa (FARA) and its
member organizations calls for an annual growth rate of 6% in agricultural productivity
by 2020 to achieve sustainable development (FARA 2006). Given the current trends in
agricultural growth, achieving this annual growth rate is a major challenge that has been
worsened by climate change and variability (World Bank 2011).
12.1.2 c
onservation
a
griculture
The CA approach involves use of the combined application of organic and mineral
resources, resilient germplasm, and nutrient cycling and conservation (Vanlauwe
et al. 2010). It is reported to be an overarching approach to restoring and main-
taining soil productivity, and results into synergy and improved conservation and
