Chemistry Reference
In-Depth Information
ISFM is derived from Sanchez's earlier 'Second Paradigm' but uses fertiliser
as the entry point for improving crop productivity. It asserts that substantial
and necessary organic resources may be derived as by-products of food crops
and livestock enterprise. ISFM also recognises the importance of an enabling
environment that permits farmer investment in soil fertility management, and
the critical importance of farm input suppliers and fair produce markets,
favourable
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policies,
and
properly
functioning
institutions,
particularly
agricultural extension.
3 Availability and Quality of Organic Resources in
African Farming Systems
Before addressing the main theme of this chapter, it is important to stress some
important notions related to organic matter quality and availability in African
farming systems, since these determine some of the boundary conditions within
which ISFM necessarily resides.
3.1 The Organic Resource Quality Concept
Although organic inputs had not been new to tropical agriculture, the first
seminal synthesis on organic matter management and decomposition was
written only in 1979.
12
Between 1984 and 1986, a set of hypotheses was
formulated based on two broad themes, 'synchrony' and 'soil organic matter
(SOM)', building on the concepts and principles formulated in 1979. Under the
first theme, especially the O(Organisms)-P(Physical environment)-Q(Quality)
framework for OM decomposition and nutrient release, formulated earlier,
was worked out and translated into hypotheses driving management options to
improve nutrient acquisition and crop growth. Under the second theme, the
role of OM in the formation of functional SOM fractions was stressed. During
the 1990s, the formulation of the research hypotheses related to residue quality
and N release led to a vast number of projects aiming at validation of these
hypotheses, commonly resulting in meaningful relationships between N release
dynamics and the organic resource quality, expressed as various combinations
of its N, soluble polyphenol and lignin contents.
Two major events further accentuated the relevance of organic resource
quality in tropical soil fertility management. Firstly, a workshop was held in
1995 with its theme 'Plant litter quality and decomposition' resulting in a book
summarising the state of the art of the topic.
13
Secondly, the Tropical Soil
Biology and Fertility Institute (TSBF) in collaboration with its national
partners and Wye College developed the Organic Resource Database (ORD)
and related Decision Support System (DSS) for OM management.
14
The
Organic Resource Database contains information on organic resource quality
parameters, including macronutrient, lignin and polyphenol contents of fresh
leaves, litter, stems and/or roots from almost 300 species found in tropical
agro-ecosystems. Careful analysis of the information contained in the ORD led
