Chemistry Reference
In-Depth Information
appropriate use of external inputs, be it fertilisers, lime, or irrigation water, was
believed to be able to alleviate any constraint to crop production. Following this
paradigm, together with the use of improved cereal germplasm, the 'Green
Revolution' boosted agricultural production in Asia and Latin America in ways
not seen before. Organic resources were considered less essential.
Because the 'Green Revolution' by-passed sub-Saharan Africa (massive
applications of fertilisers and pesticides resulted in environmental degradation in
Asia and Latin-America, and fertiliser subsidies were abolished in SSA, imposed
by structural adjustment programs), a renewed interest in organic resources
could be observed in the early 1980s. The balance shifted from mineral inputs
only to low mineral input sustainable agriculture (LISA), where organic
resources were believed to enable sustainable agricultural production. Because
LISA systems did not emphasise the need for fertiliser, organic resources were
merely considered as short-term sources of nutrients, especially N. After a
number of years of investment in research activities evaluating the potential of
LISA technologies, such as alley cropping or live-mulch systems, several
constraints were identified both at the technical (e.g. lack of sufficient organic
resources) and the socio-economic level (e.g. labour-intensive technologies).
In this context, the Second Paradigm for tropical soil fertility research was
formulated as: 'Rely more on biological processes by adapting germplasm to adverse
soil conditions, enhancing soil biological activity and optimising nutrient cycling to
minimise external inputs and maximise the efficiency of their use' (see Table 1).
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This paradigm did recognise the need for both mineral and organic inputs to
sustain crop production, and emphasised the need for all inputs to be used
efficiently. The need for both organic and mineral inputs was advocated because
(i) both resources fulfil different functions to maintain plant growth; (ii) under
most small-scale farming conditions, neither of them is available or affordable in
sufficient quantities to be applied alone; and (iii) several hypotheses could be
formulated leading to added benefits when applying both inputs in combination.
The second paradigm also highlighted the need for improved germplasm; as in
earlier days, more emphasis was put on the nutrient supply side without worrying
too much about the demand for these nutrients. Obviously, optimal synchrony or
use efficiency requires both supply and demand to function optimally.
The need for sustainable intensification of agriculture in SSA and the
recognition that this cannot happen without fertiliser has recently gained strong
support, in part because of the growing recognition that farm productivity is a
major entry point to break the vicious cycle underlying rural poverty. Recent
landmark events include the African Heads of State Fertiliser Summit held in
Abuja, Nigeria,
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and the launching of the Alliance for a Green Revolution in
Africa (AGRA). Kofi Annan, the chairman of the board of AGRA, has
repeatedly stressed that the African Green Revolution should be uniquely
African by recognising the continent's great diversity of landscapes, soils,
climates, cultures and economic status, while also learning lessons from earlier
Green Revolutions in Latin America and Asia.
11
Since fertiliser is an expensive
commodity, AGRA has adapted Integrated Soil Fertility Management (ISFM)
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