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Fig. 3. Temporal variations of (a) microbial biomass C (0–12 cm); (b) soil K2SO4–extractable C (0–12 cm), (c) soil-surface CO2 flux, and (d) cumulated CO2 emissions at day of year (DOY) 174 (23 June 1999) for a loam soil cropped to maize and amended with ammonium nitrate fertilizer (NH4–NO3), and pig slurry applied in the fall (fall slurry) or in the spring (spring slurry). Fall application of slurry was made on 13 Oct. 1998, and ammonium nitrate and spring slurry were applied on 17 May 1999. Error bars represent the LSD (P = 0.05) for treatment comparison at each date.
