Enhancing soil microbial biomass and enzyme activities through integrated organic-inorganic fertilization for improved disease-suppressive potential in gypsiferous soils of Northern Iraq
Abstract
Soil biological health is significantly affected by fertilization approaches, mainly under intensive agricultural systems. The current study assessed the impacts of organic, inorganic, and integrated nutrient management (INM) strategies on important soil microbial and biochemical parameters to ascertain sustainable fertilization alternatives that improve soil functioning. The justification was to assess whether integrating organic and mineral fertilizers provides synergistic benefits for soil microbial activity, efficiency, and diversity compared with single-source fertilization. The findings revealed that INM (T4) constantly outclassed all other treatments. Microbial biomass carbon was highest in T4 (410 mg C kg⁻¹), followed by organic (T2) and inorganic (T3) treatments, representing better microbial environment and substrate availability under combined fertilization. Dehydrogenase and urease activities were also significantly better in T4; showing enhanced microbial metabolism, nitrogen mineralization, and enzymatic functioning due to the collective supply of labile carbon and mineral nutrients. Basal respiration peaked under T4, indicating increased microbial activity and carbon cycling, while remaining within a range indicative of better soil fertility rather than microbial stress. The microbial metabolic quotient (qCO₂) was lowest in T4, proposing higher microbial efficiency and reduced carbon loss per unit biomass. Furthermore, microbial diversity, determined by the Shannon index, was maximum under INM, showing the development of a more diverse and functionally resilient microbial community. In summary, integrated nutrient management significantly increases soil microbial biomass, enzymatic activity, metabolic efficiency, respiration, and diversity. These findings validate that integrating organic and inorganic fertilizers is a superior and sustainable approach for improving soil biological health, nutrient cycling, and long-term soil productivity.
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DOI: https://doi.org/10.33804/pp.010.01.5942
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