Biogas slurry topdressing enhances the comprehensive benefits of maize: New perspectives on grain filling process, yield, and endogenous microbiome

Finding new approaches to enhance the comprehensive effects of maize has been the persistent pursuit of scientific researchers. A three-year field experiment was conducted to elucidate the possible mechanisms or pathways of biogas slurry topdressing as replacement of chemical fertilizer (BSTR) affecting maize yield, quality, economic benefits, and endogenous microbiome. Compared with pure chemical fertilizer topdressing (CF), BSTR further increased post-tasseling dry matter (DM) accumulation, grain-filling characteristic parameters and yield components, with the increase amplitude gradually rising as the BSTR proportion increased. BSTR had greater potential to stimulate grain yield potential, with the pure biogas slurry topdressing treatment (100%BS) being the most representative, significantly increasing yield by 26.50% and 14.76% compared with the CF treatment in 2022 and 2023, respectively. The higher BSTR ratio contributed to higher net income (NP), with 100%BS increasing NP by an average of 3867.72 RMB/ha over three years compared with CF. Furthermore, grain filling and dehydration directly affected yield components, while yield and NP were primarily subject to direct feedback regulation by treatment, years, and DM accumulation and redistribution. We also found that grain endophytic bacteria were more responsive to BSTR than endophytic fungal—BSTR treatment increased ACE and Chao1 indices of grain endophytic bacteria and further adjusted the relative abundances of endophytic bacterial phyla such as Proteobacteria, Actinobacteriota, and Bacteroidota, based on CF treatment. BSTR facilitated the conservation of water and fertilizer resources and the circular reuse of agricultural waste, with 100%BS treatment being optimal for enhancing the comprehensive benefits of maize. • BSTR optimized grain filling and dry matter accumulation processes after VT, • BSTR has the potential to stimulate grain yield and improve economic benefits, • BSTR altered endophytic bacteria diversity and community composition in grains, • Endophytic bacteria in maize kernels are more sensitive than endophytic fungi.