Chemistry Reference
In-Depth Information
ways: (i) ISFM as an entry point for producing organic resources in situ,
the most viable mode of organic resource acquisition in African
smallholder systems; (ii) the occurrence of and mechanisms underlying
positive interactions between organic inputs and fertiliser, specifically
focusing on the role or organic resource quality; (iii) organic resources as
a solution to site-specific constraints, including high phosphorus
sorption, soil acidity or soil erosion; and (iv) the potential role of
organic resources in rehabilitating non-responsive soils. In a last section,
the potential impact of ISFM on soil organic matter stocks and quality
are addressed. In summary, although ISFM cannot be implemented
without organic resources, the ISFM framework takes into account the
realities of organic resource availability at the smallholder farm level.
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1 Introduction
In sub-Saharan Africa (SSA) agricultural production growth is lagging behind
population growth, resulting in decreasing per capita food production.
Moreover, in contrast with other regions in the tropics, production increases
for the major crops are the result of areas expansion rather than productivity
increases.
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Many reasons have been proposed that explain the lack of Green
Revolution-type of productivity increases in SSA, including biophysical (e.g.
the presence of old or shallow soils and the lack of geological soil
rejuvenation), economic (e.g. the high price and/or unavailability of fertiliser),
infrastructural (e.g. the absence of efficient and profitable input and output
markets), social (e.g. the perseverance of traditional beliefs related to planting
times), and political (e.g. the lack of government investment in agriculture),
with each of these likely playing a role in the persistence of the colloquially
called 'one-ton agriculture'. That said, in many areas of SSA where population
densities are too high to allow for fallow-based soil fertility regeneration
phases, intensification is a necessity to reduce rural poverty and hunger. In
other areas with lower population densities, the rural population is often
located near environmentally valuable ecosystems (e.g. the primary forest of
the Congo basin) with arguments for intensification also applying to such
areas in line with the Borlaug hypothesis that preservation of natural
ecosystems can only happen through intensification of agricultural land.
Before addressing the main topic of this chapter, it is important to sketch some
important characteristics of African smallholder farming systems. In the 1970s, it
was concluded that African soils are as variable, if not more so, as soils in other
regions.
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Such variability strongly impacts on soil fertility and its management.
At the regional scale, overall agro-ecological and soil conditions have led to
diverse population and livestock densities across SSA and to a wide range of
farming system.
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Each of these systems has different crops, cropping patterns,
soil management considerations, and access to inputs and commodity markets.
At the national level, smallholder agriculture is strongly influenced by
governance, policy, infrastructure, and security levels. Roads also play a major
