Insight into the Active Organic Nitrogen Pool Estimated by Isotopic Equilibrium Approaches
W. J. Wang*,a,
C. J. Smithb and
D. Chenc
a NR&M, 80 Meiers Rd, Indooroopilly, Brisbane, QLD 4068, Australia
b CSIRO Land and Water, GPO Box 1666, Canberra 2601, ACT, Australia
c Dep. of Resource Management and Horticulture, the Univ. of Melbourne, Parkville 3052, VIC, Australia

View larger version (33K):
[in a new window]
|
Fig. 1. Dynamics of total NO-3N (NT) and NH+4N (AT) accumulation in soils following imposition of different treatments: Treatment 1, 10 mg labeled NH+4N kg-1 only; Treatment 2, 10 mg labeled NH+4N + 1000 mg C kg-1; and Treatment 3, 100 mg labeled NH+4N + 1000 mg C kg-1. The vertical bars represent ±SD.
|
|

View larger version (24K):
[in a new window]
|
Fig. 2. Dynamics of labeled N in NO-3 (NL) and NH+4 (AL) pools of Soil 1 after different treatments: Treatment 1, 10 mg labeled NH+4N kg-1; Treatment 2, 10 mg labeled NH+4N + 1000 mg C kg-1; and Treatment 3, 100 mg labeled NH+4N + 1000 mg C kg-1. The vertical bars represent ±SD.
|
|

View larger version (26K):
[in a new window]
|
Fig. 3. Dynamics of labeled N in NO-3 (NL) and NH+4 (AL) pools of Soil 2 after different treatments: Treatment 1, 10 mg labeled NH+4N kg-1; Treatment 2, 10 mg labeled NH+4N + 1000 mg C kg-1; and Treatment 3, 100 mg labeled NH+4N + 1000 mg C kg-1. The vertical bars represent ±SD.
|
|

View larger version (30K):
[in a new window]
|
Fig. 4. Changes in the labeled to total N ratios in NO-3 (NL/NT) and NH+4 (AL/AT) pools during incubation of Soil 1, following three different treatments: Treatment 1, 10 mg labeled NH+4N kg-1; Treatment 2, 10 mg labeled NH+4N + 1000 mg C kg-1; and Treatment 3, 100 mg labeled NH+4N + 1000 mg C kg-1. The vertical bars represent ±SD.
|
|

View larger version (30K):
[in a new window]
|
Fig. 5. Changes in the labeled to total N ratios in NO-3 (NL/NT) and NH+4 (AL/AT) pools during incubation of Soil 2, following three different treatments: Treatment 1, 10 mg labeled NH+4N kg-1 only; Treatment 2, 10 mg labeled NH+4N + 1000 mg C kg-1; and Treatment 3, 100 mg labeled NH+4N + 1000 mg C kg-1. The vertical bars represent ±SD.
|
|

View larger version (26K):
[in a new window]
|
Fig. 6. The active organic N pool as affected by treatment, incubation time, and the equation used for estimation. Estimates on or after the symbols marked with arrows were based on AL (labeled NH+4N) and Qe (15N abundance of a N pool at the time of sampling during incubation) of the NH+4 pool. Treatments are as follows: Treatment 1, 10 mg labeled NH+4N kg-1; Treatment 2, 10 mg labeled NH+4N + 1000 mg C kg-1; and Treatment 3, 100 mg labeled NH+4N + 1000 mg C kg-1. The vertical bars represent ±SD.
|
|
Copyright © 2003 by the Soil Science Society of America.