[Priming Effects of Soil Moisture on Soil Respiration Under Different Tillage Practices]
In the early stage of an incubation experiment, soil respiration has a sensitive response to different levels of soil moisture. To investigate the effects of soil moisture on soil respiration under different tillage practices, we designed an incubation trial using air dried soil samples collected from tillage experiment station established on black soils in 2001. The tillage experiment consisted of no tillage (NT) ridge tillage (RT) and conventional tillage (CT) According to field capacity (water holding capacity, WHC) we set nine moisture levels including 30% 60% 90% 120% 150% 180% 210% 240% 270% WHC. During the 22 day short term incubation, soil CO2 emission was measured. In the early stage of incubation, the priming effects occurred under all tillage practices. There were positive correlations between soil respiration and soil moisture. In addition to drought and flood conditions, soil CO2 fluxes followed the order of NT RT CT. We fitted the relationship between soil moisture and soil CO2 fluxes under different tillage practices. In the range of 30% 270% WHC, soil CO2 fluxes and soil moisture fitted a quadratic regression equation under NT, and linear regression equations under RT and CT. Under the conditions of 30% 210% WHC of both NT and RT, soil CO2 fluxes and soil moisture were well fitted by the logarithmic equation with fitting coefficient R2 0.966 and 0.956, respectively.
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