Effects of compound microbial fertilizer combined with potassium fulvic acid on soil physicochemical properties, microbial community structure, and cotton productivity in saline-alkali soil

Abstract

To explore the effects of compound microbial fertilizer (containing Lactobacillus acidophilus and Corynebacterium glutamicum) combined with potassium fulvic acid on cotton growth and soil ecology in Xinjiang saline-alkali soil, a two-year field experiment with seven treatments was conducted in a randomized block design. We analyzed cotton emergence rate, yield components, rhizosphere soil physicochemical properties (pH, water-soluble salts, major ions), and soil microbial community structure using high-throughput sequencing. Results showed that HT5 (150 L·hm⁻² microbial fertilizer + 15 L·hm⁻² potassium fulvic acid) significantly increased cotton emergence rate to 85.00%. HT4 (120 L·hm⁻² microbial fertilizer + 15 L·hm⁻² potassium fulvic acid) achieved the highest yield increase of 13.31% compared with the fulvic acid-only control. Application of microbial fertilizer effectively reduced soil pH, water-soluble salt, Cl⁻, and Na⁺ contents, and the improvement effects were enhanced with increasing application rate. Bacterial diversity was relatively stable among treatments, while fungal diversity and the relative abundance of beneficial fungi such as Pseudeurotium and Mortierella increased significantly. Overall, compound microbial fertilizer combined with potassium fulvic acid improved soil physicochemical conditions, optimized rhizosphere microbial community structure, and enhanced cotton growth and yield under saline-alkali conditions. The HT4 treatment was identified as the optimal application scheme under the experimental conditions, providing a feasible strategy for high-quality and high-yield cotton production in Xinjiang saline-alkali soils.