3. Results
3.1. Techno-sphere emissions
Simulated sequestered carbon and cumulative N2O emissions
are presented in Fig. 2. Carbon sequestration under CT shows little
change over the 30-year simulation time. In general, NT carbon
sequestration was higher than RT. The amount of sequestered soil
carbon started to level off for the highest rainfall zone by the end of
the simulation period at year 30. Starting the simulation from the
stable content for CT at 104.7 Mg C ha1
, NT began to level off at
108.8 Mg C ha1 storing 4.1 Mg C ha1 in 30 years. In the intermediate
rainfall zone, the sequestered carbon did not level off by the
end of the simulation and the stored carbon in 30 years was about
2.1 Mg C ha1
. The initial soil carbon for the middle rainfall zone
was less than half that for the high rainfall zone. As shown by
the sawtooth pattern, sequestered carbon dropped during fallow
years and was higher during years of crop production and in proportion
to biomass yield, e.g. higher in wheat than barley. For the
low rainfall zone only RT is typically used by farmers, and the simulation
showed 1.5 Mg C ha1 stored within the simulated period
of 30 years. The cumulative N2O results increased linearly in all tillage,
rainfall and rotation scenarios. Simulations of N2O emissions
for CT were higher in the high rainfall zone compared to NT and
RT but relative emissions decreased as rainfall declined.
3.2