Abstract:
Effects of wet/dry cycles in inducing greenhouse gas emissions are well
documented. However, the effects of field drying and rewetting events remain
poorly understood. This study investigated the impact of irrigation and effluent
application on CO2
, N2
O and CH4
in the Waimate District of New Zealand. Four soil
management practices: (i) only added effluent, (ii) only added water, through irrigation,
(iii) effluent and water added together, and (iv) neither water nor effluent
added were sampled using static headspace chambers with a chamber diameter
of 250 mm and height of 150 mm. All locations were sources of CO2
and N2
O but
net sinks of CH4
. Carbon dioxide fluxes ranged from 4.38 to 14.49 mg CO2
-C m−2 hr−1
while those for N2
O were between 0.007 and 0.012 mg N2
O-N m−2 hr−1. Wetting soils
receiving effluent enhanced CO2
production by 161%, suppressed N2
O fluxes by 17%
but increased CH4
uptake by 286%. When compared with control locations, effluentonly
locations observed 50% less CO2
, yet highest N2
O emissions were observed on
the same locations. Nitrous oxide emissions were positively correlated with CO2
but negatively correlated with CH4
emissions. Irrigation-only locations had 33% more
earthworms than effluent locations. Maximum density and biomass occurred where
both effluent and irrigation were applied. There was no evidence of relationships
between earthworm measurements and gas fluxes.
