Improving soil structure and function for continuous cropping of sweet melon using microalgae-based biological fertilizer

Melon occupies an important position in fruits and vegetables production and consumption in China for its rich nutrient content. However, continuous cultivation of melons is characterized by disorders such as soil nutrient reduction and microbial community imbalance. This paper was the first to investigate the effects of algae-based biofertilizers (Chlorella vulgaris and shell powder, TQB; Chlorella vulgaris and straw fermentation liquid, TQJ; and Chlorella vulgaris and Bacillus sphaericus, TQY) on the physicochemical characteristics and microbial community structure of the soil for potted continuous-cropped melons. The results showed that, compared with the control group (with water only, TC), the three algae-based biofertilizers substantially increased the important elements of carbon (C), nitrogen (N), sodium (Na), and potassium (K) in melon soil. The algae-based fertilizer TQY had the greatest impact, increasing the ammonia nitrogen (NH₄⁺-N) content by 437.5 %. Also, the salinity indexes, Na⁺ and K⁺, were enhanced by 416.7 % and 45 % respectively. Notably, the application of algae-based biofertilizer was found to increase the abundance of beneficial bacteria such as Chloroflexi and Firmicutes, and reduce the fungi, further improve the adverse factors caused by continuous cropping obstacles of sweet melon. This study would provide technical support for soil improvement to enhance the continuous growth and quality of melon production.