Agriculture Reference
In-Depth Information
Among several strategies of managing soil fertility are effective erosion control,
alternative nutrient sources, and nutrient cycling (Fonte et al. 2012). In general, soil
fertility decreases with increase in distance from the homestead (Zingore et al. 2008).
All forms of organic wastes are considered as “organic treasures” and recycled as
organic fertilizers (Yang 2006). Yet, a judicious use of inorganic fertilizers can be
important in improving soil fertility (Masvaya et al. 2010). Soil fertility management
technologies on small landholder farms in SSA include farming systems based on
the combined use of BNF, recycling of organic wastes, and judicious use of mineral
fertilizers (Bekunda et al. 2010; Chikowo et al. 2010; Kanyama-Phiri et al. 1998).
Green manure (with
Sesbania
) has been found useful in improving the lability
of soil organic C (SOC) pool compared with FYM and crop residues (Verma et al.
2010). With long-term application and at high rates, use of organic manures can
improve soil quality and agronomic productivity (Datta et al. 2010). Cover crop-
ping and mixed cropping (cassava and cover crops) techniques are used to enhance
fertility of Colombian hillside soils of low fertility (Daellenbach et al. 2005). In
sandy loam soils of the humid tropics, agroforestry (alley cropping) systems could
effectively substitute slash-and-burn systems by adding up to 10 Mg/ha of C in the
litter layer (Aguiar et al. 2009). Similar to other options of soil management, agro-
forestry techniques are also site specific in their relevance, performance, and farmer
acceptability (Cooper et al. 1996). Use of leguminous trees and cover crops can
enhance BNF so that plants can utilize the N
2
available in air (Shiferaw et al. 2004).
A study on smallholder perception of agroforestry conducted in Panama by Fischer
and Vasseur (2002) indicated that among obstacles to adoption of agroforestry tech-
niques are insufficient extension, inappropriate project design or management (e.g.,
top-down approach), economic constraints, and policy issues.
Furthermore, the processes of nutrient depletion and soil fertility decline are spa-
tially heterogeneous (Tittonell et al. 2005). This spatial heterogeneity is caused by
biophysical and socioeconomic factors. Precision agriculture or soil-specific farm-
ing can be used for spatial and temporal optimization of fertilizers and other input
(Booltink et al. 2001). Use of precision agriculture enables farmers to use different
management practices within a single variable field. Such technology can be used
even in small farms such as those in Kenya and Costa Rica (Booltink et al. 2001).
1.6 EROSION CONTROL
Accelerated soil erosion has plagued small landholders, who often cultivate sloping
and marginal lands. Up-and-down cultivation and mechanical seedbed preparation
exacerbate the erosion hazard. Thus, soil erosion is a serious hazard, especially in
erosional hotspots (e.g., the Loess Plateau in Northwest China, the Himalayan region,
West Africa/Sahel, East African highlands, Andean region, and the Caribbeans).
Accelerated erosion depletes SOC concentration and plant nutrients, truncates the
topsoil, and wastes water as surface runoff. Conventional agriculture and extractive
farming can exacerbate erosion in erodible lands (Kong et al. 2002). Yet, intensifica-
tion because of high demographic pressure can reduce erosion (Tiffen et al. 1994;
Sahrawat et al. 2010). Integrated use of soil and water conservation practices in con-
junction with balanced plant nutrients on a watershed scale can enhance soil quality,
