Agriculture Reference
In-Depth Information
Chemical Weathering, Reactive
Transport and C-N Dynamics
manipulation of vegetation/crop (e.g. crop
rotation, nitrogen-fixing plants, intercrop-
ping), is the starting point of a series of bio-
geochemical mechanisms and processes that
all together comprise the abovementioned
soil functions and soil services including
water filtration and transformation. Soil car-
bon is the key driver of soil structure that
provides water regulation and drainage, and
is the main substance controlling soil bio-
geochemistry and thus affecting water trans-
formation reactions. The physical role of
organic carbon on soil hydraulic properties
including macropore development and water-
holding capacity is also a factor.
Water, as it moves along a hydrologic
pathway, alters the chemical composition of
not only the soil and rock that come in con-
tact but also its own composition. A concep-
tual schematic of the predominant hydrologic
transport processes and soil characteristics
affecting solute transport is presented in
Fig. 8.1 (adapted from Kohne et al ., 2009a,b).
The figure illustrates a vertical cut of the un-
saturated soil along a hill slope. Hydrologic
processes that control the drainage charac-
teristics of soil, and in turn its soil moisture,
The Thematic Strategy for Soil Protection
prepared for the European Union (EU) has
identified soil ecosystem functions and ser-
vices as important to the global economy and
human sustenance (European Commission,
2006). These services go beyond the most
easily identified service of biomass (food and
fibre) production, and includes carbon and
nitrogen sequestration, preservation of ter-
restrial biodiversity and the gene pool, water
filtration-transformation, provision of raw
materials, landscape and heritage (Banwart
and SoilTrEC Partners, 2011; Banwart et al .,
2011). Water filtration and mass transform-
ation of transported substances (collectively
termed below as water filtration and trans-
formation) such as nutrient ions or dissolved
pollutants are an important soil service for
the regulation and provision of clean water,
essential to human sustenance.
Organic carbon addition to the soil,
either through natural (above- and below-
ground vegetation inputs), allochtonous in-
puts (i.e. compost, green manure, manure) or
Evapotranspiration
Surface runoff
Infiltration
Macropores:
Root uptake
Root holes
Fractures
Earthworm burrows
Soil matrix:
Homogeneous
Heterogeneous-mixed
permeability
Groundwater recharge
Fig. 8.1. Hydrologic transport processes and soil characteristics affecting solute transport. (From Kohne
et al ., 2009a,b.)
 
 
 
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