Agriculture Reference
In-Depth Information
G.Cadischand K.Giller
Roles of Residue Quality in C Sequestration and N Supply
3
Soil Organic Matter
Management: The Roles of
Residue Quality in C
Sequestration and N Supply
G. C
ADISCH
1
AND
K. G
ILLER
2
1
Department of Biology,Imperial College at Wye, Wye, Ashford,
Kent TN25 5AH, UK; and
2
Department of Soil Science
and Agricultural Engineering, University of Zimbabwe, Box MP167,
Mt Pleasant, Zimbabwe
Soil Organic Matter Management for What Purpose?
The transformations of residues into soil organic matter are regulated by
three interacting factors, the physicochemical environment and resource
quality acting through decomposer communities (Swift
et al
., 1979). Hence
the quantity, the quality and the functional attributes of organic residues
are key elements for managing decomposition of soil organic matter (SOM)
and nutrient release. Here we will focus on the roles of SOM for different
management purposes paying particular attention to the time scale within
which potential interactions occur (Table 3.1). The choice of organic
resource quality is governed primarily by a particular management objective
and resource availability. Hence the classification of resource quality into
'high' and 'low' is somewhat arbitrary depending on the desired effect. For
example, residues of low C : N ratio, low lignin and polyphenol content can
be termed 'high' quality when fast nitrogen release is required, but the same
residues are 'low' quality if the desired outcome is C sequestration.
The Role of Residue Quality in C Sequestration
Atmospheric C budgets that ignore the possibility of terrestrial ecosystems
to sequester C do not balance, and indicate that there is a 'missing sink'
of ~0.4-4 Gt C year
−1
(Gifford, 1994). It has been suggested that the
terrestrial biosphere (vegetation and soils) can act as a source as well as a
sink of organic C. Land clearing, mostly by tropical deforestation, has been
Search WWH ::
Custom Search