Effect of bio-organic fertilizers partially substituting chemical fertilizers on labile organic carbon and bacterial community of citrus orchard soils.

Aims: For the sustainable development of agroecosystems in citrus orchards, we studied the short-term effects of bio-organic fertilizer substitution for chemical fertilizers on the dynamic changes in the soil environment. Methods: We carried out a field experiment in citrus orchards. Five treatments were set up with a duration of six months and the substitution ratio was based on equivalent nitrogen substitution. Soil properties, soil labile organic carbon, and soil bacteria were measured and analyzed. Results: Bio-organic fertilizers substituting chemical fertilizers could significantly increase soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), dissolved organic carbon (DOC), and easily oxidized organic carbon (EOC) content (P < 0.05). The carbon pool management index (CPMI) was the largest in 75% bio-organic fertilizer treatment. In addition, the substitution of chemical fertilizers with bio-organic fertilizers significantly increased the alpha diversity of bacterial communities, with a maximum Shannon index of 9.78 for SF75. The relative abundance of Actinobacteria, Actinobacteria and Bacteroidetes was higher than that of CK, while the relative abundance of Acidobacteria and Choloflexi was lower than that of the control group. Redundancy analysis showed that DOC, CPMI, available potassium (AK), and nitrate-nitrogen (NO3−-N) were the main driving factors affecting the bacterial community structure. The highest expression abundance of metabolic pathways in soil bacteria was predicted by KEGG to exist. Conclusion: We conclude that the appropriate application of bio-organic fertilizer improved soil properties and reshaped bacterial ecology and 75% bio-organic fertilizer is a promising fertilization practice for citrus orchard soils. [ABSTRACT FROM AUTHOR]