The role of organic/bio-fertilizer amendment on aggregate stability and organic carbon content in different aggregate scales

- Application of bio-fertilizers increased soil aggregate stability in macro and micro aggregate scales.
- Bio-fertilizer and vermicompost increased OC content in both aggregate scales.
- Bio-fertilizer application combined with vermicompost supports the stability and OC content of aggregates to a far greater extent.
- The weak correlation between OC content and aggregate stability may be due to high clay and lime content of the soil.

This study investigated the effects of different organic and bio-fertilizer (alone or in combination) applications on aggregate stability and organic carbon (OC) content in macro (2-1 mm) and micro (0.25-0.050 mm) aggregate sizes of clay loam (Typic Xerofluvent) textured soil. In addition, correlation between OC content and aggregate stability was determined. The study was conducted as a pot experiment under greenhouse conditions and was arranged in a completely randomized design with three replications. The treatments were: control (no fertilizer) (C), inorganic fertilizer (15:15:15 compound fertilizer + ammonium nitrate, 33% N) (F), mycorrhizal fungi (Glomus spp.) (M), microalgae (Chlorella spp.) (A), bacteria (Bacillus megaterium KBA-10 + Pantoea agglomerans RK-134 + Pseudomonas fluorescens FDG-37) (BMF), bacteria (Bacillus subtilis PA1 + Paenibacillus azotofixans PA2) (BCP), vermicompost (V), vermicompost + mycorrhizal fungi (VM), vermicompost + microalgae (VA), vermicompost + bacteria (VBMF) and vermicompost + bacteria (VBCP) applied in 90 days incubation period. At the end of the 90-day incubation period, organic and bio-fertilizer amendments had an increasing impact on aggregate stability and OC content in macro- and micro- aggregate scale. Especially, bio-fertilizers in combination with vermicompost mostly had stronger effects on stability and OC content of aggregates of both size classes in comparison with control and bio-fertilizer treatments alone. In addition, significant (p < 0.05) and positive correlations were observed between stability and OC contents of macro (2-1 mm) and micro (0.25-0.050 mm) aggregates size classes in each treatment.