Soil Respiration under Maize Crops: Effects of Water, Temperature, and Nitrogen Fertilization

To evaluate the response of soil respiration to soil moisture, temperature, and N fertilization, and estimate the contribution of soil and rhizosphere respiration to total soil CO2 emissions, a field experiment was conducted in the Fengqiu State Key Agro-Ecological Experimental Station, Henan, China. The experiment included four treatments: bare soil fertilized with 150 kg N ha−1 (CK), and maize (Zea mays L.)-cropped soils amended with 0 (N0), 150 (N150), and 250 (N250) kg N ha−1 Mean seasonal soil CO2 emissions in the CK, N0, N150, and N250 treatments were estimated to be 294, 598, 541, and 539 g C m−2, respectively. The seasonal soil CO2 fluxes were significantly affected by soil temperature, with the change in the rate of flux for each 10°C increase in temperature (Q10) of 1.90 to 2.88, but not by soil moisture. Nitrogen fertilization resulted in a 10.5% reduction in soil CO2 flux; however, it did not significantly increase the maize aboveground biomass but did increase maize yield. Soil respiration measurement using the root-exclusion technique indicated that soils fertilized with 150 kg N ha−1 contributed 54% of the total soil CO2 emission, or 8% of soil organic C down to a depth of 40 cm. An amount of C equivalent to 26% of the net assimilated C in harvested above- and belowground plant biomass was returned to the atmosphere by rhizosphere respiration.