Conventional manure and bio-organic fertilizer application improve soil quality and cotton yield through distinct enrichment of beneficial microorganisms in arid saline areas

Crop yield is significantly influenced by the application of different types of organic fertilizer. However, under equivalent carbon input conditions, the mechanisms through which different organic fertilizer types affect soil properties and cotton ( Gossypium hirsutum L.) yield in arid saline soils remain unclear. Therefore, this study aimed to investigate the effects of conventional manure and bio-organic fertilizer application on soil properties and cotton yield in severe saline-alkali soil of arid regions. Based on equivalent carbon input, a field experiment was conducted with five treatments (no organic fertilizer application (CK), application of 37.5 t·ha −1 (COF1) and 52.5 t·ha −1 (COF2) conventional manure, 18 t·ha −1 (BOF1) and 25.5 t·ha −1 (BOF2) bio-organic fertilizer). Results showed that compared with CK, the COF2 and BOF2 treatments reduced surface soil soluble salt content by 13.77% and 13.17%, respectively, and increased cotton yield by 57.94% and 51.51%, respectively. These improvements were attributed to enhanced soil aggregate stability and promoted leaching of soil salts. Concurrently, fertilization increased the content of soil available nitrogen and potassium. Notably, BOF was superior to COF in improving soil aggregate stability, whereas COF outperformed BOF in enhancing soil available nutrients. This was primarily attributed to the distinct enrichment of beneficial microorganisms in the cotton rhizosphere by COF and BOF treatments. Specifically, the enrichment of Pseudomonadota may promote soil nutrient activation, while the enrichment of Actinomycetota may improve soil aggregate stability. This study provides a theoretical basis for ameliorating saline-alkali soils and enhancing crop yield in arid regions.