Abstract:

To alleviate the deficiency of available silicon in soil, this study explored the synergistic desilication mechanism between attapulgite and silicate bacteria, and verified their effects on soil improvement, fertility regulation, growth promotion and yield enhancement. The previously screened silicate strain APT-28 was immobilized on raw and purified attapulgite. Structural characterizations of mineral materials before and after bacterial immobilization were performed, and field experiments were carried out to clarify their practical application efficacy. The results indicated that purification treatment could effectively remove the blocky impurities in attapulgite, increase the specific surface area, micropore area and crystallinity. The adhesion and lattice embedding of the bacterial strains on the surface of attapulgite did not destroy its main crystal structure. Both purification and loading of bacteria can increase the silicon (Si) content in bentonite. After loading with bacteria, the Si content of the purified ore reached 86.59%. X-ray diffraction (XRD) showed that all samples had good crystallinity, with peak intensities in the order of A-C > A-C-J > A-Y > A-Y-J, and bacterial loading caused lattice contraction. Field experiments showed that the treatment with raw attapulgite-based bio-silicon fertilizer (A-Y-J) yielded the highest pakchoi output, reaching 104639.05 kg/hm², with an increase of 29.56% relative to the control. Meanwhile, the contents of vitamin C and silicon in pakchoi were significantly elevated. Soil available silicon content reached 198.03 mg/kg under the treatment of purified attapulgite bio-silicon fertilizer (A-C-J), which was 13.37% higher than that of the control. The synergistic interaction between attapulgite and silicate bacteria effectively increased soil contents of organic matter, total nitrogen and other nutrients. Correlation analysis revealed that silicon accumulation in pakchoi exhibited an extremely significant positive correlation with crop yield and vitamin C content (P<0.01). This study clarified the synergistic desilication mechanism of attapulgite combined with silicate bacteria, which can provide a theoretical reference and scientific support for the research and popularization of new-type biological silicon fertilizers.

Key words: attapulgite, silicate bacteria, structural characterization, biological silicon fertilizer, soil nutrients, quality and yield