Organic and Inorganic Nutrient Sources Effects on Soil Microbial Activity in Cultivated Soil

Background and Objective: Excessive use of inorganic fertilizers to boost crop yields often leads to resource wastage, environmental pollution, and long-term soil degradation, necessitating sustainable alternatives. This study evaluated the effects of organic (Super Gro, poultry manure, pig manure) and inorganic (NPK) nutrient sources on soil microbial activity and related parameters following incubation of cultivated soil. Materials and Methods: Soil respiration, microbial metabolic quotient (qCO₂), carbon mineralization quotient (qM), microbial biomass carbon to organic carbon ratio (Cmic:Corg), and microbial carbon change rate quotient (qC) were measured at 3, 6, 9, and 12 days after incubation (DAI). Data collected from the experiment were subjected to Analysis of Variance (ANOVA), and treatment means were compared using the Tukey test at a 5% significance level. Results: Results showed that Super Gro significantly increased soil respiration and cumulative CO₂-C production at 3 DAI compared to other treatments and the control, while NPK recorded the lowest CO₂ evolution by the experiment’s end. Organic amendments elevated qCO₂, indicating microbial stress, and enhanced carbon immobilization, whereas inorganic fertilizers suppressed microbial activity over time. No significant differences in qM or Cmic:Corg were observed among treatments by 12 DAI, though organic sources consistently supported higher microbial activity. Negative qC values at 6 and 9 DAI suggested carbon loss, which diminished by 12 DAI. Conclusion: This study underscores the potential of integrating organic nutrient sources to enhance soil health and promote sustainable agriculture.