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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