Agriculture Reference
In-Depth Information
Results
Production of CO 2 and 14 CO 2
The production of CO 2 was greatest in the undrained soil and least in
the soil drained for 1 year. Approximately 19, 18, 25 and 25% of the soil
organic matter mineralized within 97 days in the undrained soil and soils
drained for 1, 5 and 8 years, respectively. The production of 14 CO 2 showed
the same pattern in each soil; an increase in the first days of incubation,
reaching a maximum with no further production thereafter (Fig. 3.12.1a).
The rate of increase and the time at which the maximum value was
attained, however, changed from soil to soil. Approximately 36, 36 and
38% of the glucose C added was evolved as 14 CO 2 in the undrained soil and
soils drained for 1 and 5 years, respectively, but the amount was 60% in the
soil drained for 8 years. The difference in CO 2 production between the
untreated soil and the soil treated with 14 C-labelled glucose was greater in
soil drained for 1 year than in the other soils (Fig. 3.12.1b).
Inorganic N
Concentrations of NH 4 + in the untreated samples were variable over the
first 14 days of incubation without a clear pattern, and became undetect-
able in each soil thereafter. Concentrations of NH 4 + in the glucose-treated
soil sharply decreased within the first day and were undetectable or small
after 14 days (Fig. 3.12.2a). Concentrations of NO 3
in the untreated
Fig. 3.12.1. (a) Cumulative 14 CO 2 production and (b) difference in CO 2 production between the
glucose-treated and the untreated soil (mg C kg 1 dry soil) in soil from an undrained site ( w ) and
sites drained for 1 ( v ), 5 ( q ) and 8 years ( r ) treated with 1000 mg of 14 C-labelled glucose C kg 1
dry soil and 200 mg of NH 4 + -N kg 1 dry soil incubated aerobically at 22 ° C for 97 days.
Search WWH ::




Custom Search