Agriculture Reference
In-Depth Information
Table 3.3.1.
Decay constants, C and N contents for PMS addition (RPM and DPM), initial (day
165) mineral N and soil organic matter conditions (BIO, NOM, POM and IOM) for MOTOR.
Pool
Decay constant day
−
1
Initial pool size mg C kg
−
1
soil
C : N
Nmg kg
−
1
soil
PMS addition
RPM
0.035
a
4 222(
K)
2,
b
3,820
b
—
28
DPM
0.035
c
42 (K)
22,
b
652
d
4.3
150
Mineral N
88
Initial soil conditions
BIO
0.007
4 2(K
d
)
22,
117
4
.3
—
NOM
0.0012
4 (K
d
)
2,
1,000
10
.3
—
POM
0.003 (K
a
)
0.00004 (K
d
)
10,292
15
.3
—
X
22,975
15
.3
—
IOM
0
.00004 (K
d
)
22,
597
17
.3
—
Mineral N
10
a
Value reduced by fibre content according to Equation 2.
b
Cellulose and chemical additives.
c
Value reduced by fibre content according to Equation 2.
d
Microbial cells and metabolites and chemical additives to paper.
unlike stabilized soil biomass, and is assumed to have the same turnover
time as plant DPM (Table 3.3.1).
A study on PMS composition (Gilboa
et al
., 2000) showed that the
total N content of the PMS from the mill used in this study (N
tot
) was made
up of urea N (~30% of N
tot
), organic additive N (2%), NH
4
+
-N (8%), and
biomass N and metabolites (60%). We used this information to estimate
the size of the pools of N and C applied as PMS.
Results and Discussion
On N0 plots, W
96
caused a complete loss of marketable yield, although
total N uptake was not affected. However, on N1 plots, there was a highly
significant (
P
< 0.01) positive effect of W
96
on marketable yield and a
significant effect (P<0.05) on N uptake (Table 3.3.2). There was a trend
(
P
< 0.1) to higher N uptake and marketable yield with W
95
application
than with the control. Residual soil N was significantly higher in the W
96
treatment than in the control. There was a small residual effect of W
95
and a
large effect of W
96
on the N
2
O emissions. Although the C : N ratio of the
PMS was smaller than desirable to promote immobilization and prevent N
leaching, these results suggest that initial immobilization of mineral N may
have hampered initial crop development in the N0 plots.
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