Agriculture Reference
In-Depth Information
with hydrological conditions and management. Here, we report on the
amount and composition of DOC exported from grazed grasslands, and
discuss factors that modify exports, such as fertilizer management and
drainage regime.
Site Description
Most of the work reported here was carried out on the 1 ha lysimeter
plots of the Rowden Moor Drainage Experiment (Tyson
et al
., 1992)
located at the Institute of Grassland and Environmental Research, North
Wyke, Devon (NGR: SX 650995). The soil is a clayey non-calcareous
pelostagnogley
of
the
Hallsworth
series
(Dystic
Gleysol,
FAO)
(see
Armstrong and Garwood, 1991).
The experiment comprises 14 lysimeter plots of ~1 ha, grazed with
steers. Seven plots have 55 cm deep mole drains crossing 85 cm deep
permanent pipe drains, and are termed
drained
, while the remaining seven
plots are termed
undrained
. All plots have V-notch weirs for the surface plus
interflow to 30 cm depth that runs into perimeter ditches. The drained
plots have additional weirs for water that is dispersed through the drainage
system. A range of management strategies is applied to these plots, and
details of the treatments reported here are shown in Table 4.5.1 together
with treatment notation.
Quantities of DOC Exported from Grazed Grassland
In order to determine gross exports of DOC from the Rowden plots, grab
samples were taken from the weirs during the first 2 months of drainage, i.e.
Table 4.5.1.
Drainage regime, N application and number of treatments of 1 ha lysimeters,
together with treatment notation.
N application (kg N ha
−
1
year
−
1
)
Number of
Treatments
Treatment
NH
4
NO
3
Slurry
a
Drainage
Notation
High N
280
65
Undrained
HNU
2
Grass-clover
0
65
Undrained
GCU
2
Zero N
0
0
Undrained
ZNU
1
High N
280
65
Drained
HND
2
Grass-clover
0
65
Drained
GCD
2
Zero N
0
0
Drained
ZND
1
a
Slurry application ceased 1 year before the start of the current study.
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