wAbstract
@To understand the effects of nitrogen fertilization on soil respiration
in an intensively cultivated fluvo-aquic loamy soil, a field experiment
was conducted in the Fengqiu State Key Agro-Ecological Experimental
Station, Henan province, China. The experiment consisted of five
treatments: unplanted and N-unfertilized soil (CK0), unplanted
soil treated with 150 kg N ha-1 (CKNL), maize (Zea
mays L.) planted and N-unfertilized soil (N0), and planted
soils fertilized with 150 kg N ha-1 (NL) and 250 kg
N ha-1 (NH). Soil CO2 efflux during
the maize growth season was significantly affected by soil temperature
and also by soil moisture when the opposite effect of soil moisture
below and above the optimum values was distinguished. There was
a significant interdependence between soil temperature and soil
moisture in the effect on soil CO2 efflux
in the presence of maize plants. A logarithm transported regression
equation including soil temperature (T) and soil moisture (W)
was developed as y = a + bT log (W). This equation accounted for
60-71 of the seasonal variation in soil CO2
efflux, which better depicted soil CO2 efflux
than did a regression equation with soil temperature alone in
the maize planted soils. Cumulative soil CO2
emissions in the CK0 and CKNL treatments were estimated as 229}12
and 245}17 g C m-2, respectively during the experimental
period and the application of N fertilizer slightly increased
soil basal respiration by 6.5 through enhancing microbial biomass.
In contrast, cumulative seasonal soil CO2
emissions were 7.4 lower in the NL (461}33 g C m-2)
and NH (462}13 g C m-2) treatments than in the N0 treatment
(498}32 g C m-2), indicating that N fertilization marginally
significantly depressed soil respiration (p=0.06). N application
rates, however, did not exhibit any effects. Our results suggest
that the effects of N fertilization on soil respiration mainly
depended on the concentration of easily decomposed organic carbon
in soil and N fertilization possibly reduced soil respiration
in the planted soils when N released from the decomposition of
native soil organic carbon roughly met the demand for maize growth.
Keywords: Microbial biomass carbon; Nitrogen fertilization; Soil
moisture; Soil organic carbon; Soil respiration; Soil temperaturex
1. Introduction
2. Materials and methods
@2.1. Site description
@2.2. Experimental design
@2.3. Soil CO2 efflux measurement
@2.4. Maize biomass measurement
@2.5. Laboratory incubation
@2.6. Statistical analysis
3. Results
@3.1. Maize biomass
@3.2. Soil CO2 efflux
@3.3. Effects of soil temperature and moisture on soil CO2 efflux
@3.4. Effect of N addition on the decomposition of native SOC
4. Discussion
@4.1. The effect of N fertilization on soil CO2
emission
@4.2. The effects of soil moisture and temperature on soil CO2 efflux
5. Conclusions
Acknowledgements
References