Effects of Mushroom Residue Organic Fertilizer Combined with Desulfurized Gypsum on Active Organic Carbon and Its Sensitivity in Saline-Alkali Soil of the Yellow River Delta

[Objective] In order to investigate the effects of mushroom residue organic fertilizer and desulfurized gypsum on organic carbon components and carbon pool management index (CPMI) of saline-alkali soil. [Methods] The newly reclaimed wheat-maize rotation land in the Yellow River Delta was used as the research subject, and the randomized block experiment method was conducted to set up four treatments: no fertilization (CK), conventional farming fertilization (CN), mushroom residue organic fertilizer (MCOF), mushroom residue organic fertilizer and desulfurized gypsum (MCOG), which were treated by field fertilization for 3 years. [Results] The combined application of mushroom residue organic fertilizer and desulfurized gypsum significantly reduced the salinity of 0—20 cm soil layer, and increased the soil nitrogen, phosphorus and potassium nutrition content and cation exchange capacity (p