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In-Depth Information
M. Shepherdet al.
Organic Matter Management in Practice - The Potential to Reduce Pollution
3.4
Organic Matter Management
in Practice - The Potential to
Reduce Pollution
M
.
S
HEPHERD
1
, R
.
H
ARRISON
2
, R
.
M
ITCHELL
3
,
A
.
B
HOGAL
1
AND
J
.
K
ING
2
1
ADAS,GleadthorpeResearch Centre,MedenVale, Mansfield,
Nottinghamshire NG20 9PF;
2
ADAS,BoxworthResearch Centre,
Boxworth, Cambridge CB3 8NN, UK; and
3
BSES andCRC,
Peak Downs Highway, TeKowaiPMB57, Mackay MC,
Queensland 4741, Australia
Introduction
Soil nitrogen (N) supply to arable crops can be separated into a background
mineral N supply from soil organic matter (SOM) mineralization and a
'pulse' from mineralization of fresh residues (Bjarnason, 1989). Arable crop
residues can be an important source of N for the following crop (MAFF,
1994). Residue size depends on the balance between N uptake and N
removed from the field in produce, and so varies between crops (Table
3.4.1). The quality of the residue will also influence both the amount of N
mineralized and the rate of mineralization. It is clear from the quantity of
N that is potentially available (Table 3.4.1) that we need to utilize it as
efficiently as possible in the soil-crop system to minimize environmental
effects (e.g. leaching of nitrate to water courses). Here we describe experi-
ments that have measured (i) the influence of time and method of residue
incorporation on subsequent mineral N release and (ii) the contribution of
above- and below-ground residues to soil mineral N, and we discuss the
implications for efficient N management in the soil-crop system.
Description of Experiments
Standard measurement methods were used in all experiments. Nitrate
leaching was measured using porous ceramic cups (Lord and Shepherd,
1993) and estimated drainage volume (Bailey and Spackman, 1996) below
1 m. Soil mineral nitrogen (SMN) was measured (to 60 or 90 cm) by 2 M
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