Abstract:

To investigate the effects of supplementary microalgal nutrient solutions and microbial inoculants on growth and yield of soybean in the southern foothills of the Greater Khingan Range, a study was conducted from 2023 to 2024 at the soybean industrial park in Xiaomoding Village, Nierji Town, Moqi Banner, Inner Mongolia. ‘Mengke Dou 23’, a locally predominant soybean cultivar, was used as the experimental material. Four treatments were established: conventional fertilization (CK), conventional fertilization + microalgal nutrient solution (ALG), conventional fertilization + microbial agent (ARC), and conventional fertilization + microalgal nutrient solution + microbial agent (ALG+ARC). The study systematically examined the effects of these fertilization regimes on soybean agronomic traits, rhizobium abundance, seed quality, and yield. Results from the two-year experiment indicated that, compared to CK, the ALG+ARC treatment significantly increased soybean plant height by 8.41% and the number of main stem nodes by 8.71%, while significantly reducing pod height by 7.07% (P<0.05). Under the ALG+ARC treatment, the soybean root nodule count reached 92 per plant, representing a 33.33% increase compared with CK. Root nodule dry weight and plant dry matter accumulation were also significantly higher than those in other treatments (P<0.05), indicating a marked enhancement in nitrogen-fixing capacity. Grain protein and fat contents reached 40.58% and 20.51%, respectively, both of which were significantly higher than those in other treatments (P<0.05). The 100-seed weight increased to 19.85 g, and the yield reached 2919.75 kg/hm², representing a 10.45% increase compared with CK. This yield enhancement was significantly superior to that of the single-application treatments (ALG: 4.65%; ARC: 5.64%) (P<0.05). Correlation analysis revealed that soybean yield exhibited extremely significant positive correlations (P<0.01) with 100-seed weight, effective plant number, rhizobium count, number of main stem nodes, plant height, and total growth period, while showing an extremely significant negative correlation (P<0.01) with pod base height. Supplementing conventional fertilization with microalgal nutrient solutions and microbial inoculants synergistically enhances the nitrogen-fixing capacity, grain quality, and yield of soybeans cultivated in the southern foothills of the Greater Khingan Range. This provides an optimal fertilization strategy for achieving environmentally sustainable and high-yield soybean production in this region.

Key words: soybean, microalgal nutrient solution, microbial inoculant, agronomic traits, yield