Effect of co-application of straw and various nitrogen fertilizers on N2O emission in acid soil

Biochar amendment modulate microbial community assembly to mitigate saline-alkaline stress across soil depths

While microbial community assembly in saline-alkali topsoils is well-documented, distribution patterns across biochar application depths and soil layers remain unclear. This incubation study evaluated five treatment: no biochar (CK), homogeneous application (EB), and concentrated applications in upper (FB: 0-10 cm), middle (MB: 10-20 cm), or bottom layers (DB: 20-30 cm). Biochar application significantly accelerated vertical salt migration, with FB inducing 45.55 % and 61.01 % increases in water-soluble Na+ and Cl- accumulation in the bottom layer. Microbial network complexity and interspecies interactions were highest in the upper layer (edges: 926), contrasting sharply with simplified communities in deeper layer (edges ≤552). Community assembly across layers was primarily driven by salt gradients, with deep-layer communities dominated by salt-tolerant taxa (such as Halomonas and Desulfobacterota). Among treatments, FB led to the highest biomarker abundance and α-diversity. Mechanistically, FB mitigated microbial diversity loss in mid-deep layers by establishing a symbiotic consortium of salt-tolerant keystone taxa (Bacillus-Pseudomonas-Ascomycota), which enhanced stress resilience via cross-feeding. These findings demonstrate that stratified biochar application (FB) optimizes salt redistribution while fostering stress-adapted microbial consortia across soil profiles, offering a targeted strategy for saline-alkali soil remediation.

Unraveling the synergistic effect of biochar and potassium solubilizing bacteria on potassium availability and rapeseed growth in acidic soil

Potassium (K) is an essential macronutrient for plant growth. However, its bioavailability is low in acidic soils. Excessive K fertilization deteriorates the soil health, thus highlighting the need for sustainable alternatives. In previous studies, biochar application has been proven to be an effective amendment. Meanwhile, various potassium solubilizing bacteria (KSB) have been identified in soil that contributes to K bioavailability. However, their interaction under combine (co) application in acidic soil and its effects on K availability remain poorly understood. Therefore, a pot experiment was conducted to investigate the synergistic effect of co-application of rice straw biochar (BC) and KSB consortium on K availability to promote rapeseed growth. The treatment plan consisted of CK (control), recommended K fertilizer, 2 % BC (2 % w/w), KSB consortium, KSB consortium + 2 % BC (2 % w/w). Results of soil analysis conducted after crop maturity showed that co-application of 2 % BC and KSB consortium significantly improved the soil pH and organic matter contents by 0.62 and 12.52 units respectively, relative to CK. Meanwhile, soil available nutrients were greatly enhanced, as available K content increased by 52.1 %, which indicated that co-application of 2 % BC and KSB consortium could facilitate the better conversion of different forms of soil K and make it available for plant uptake. Furthermore, it also improved extracellular enzymatic activities (26.7-71.6 %) and soil bacterial community (Actinobacteriota and Firmicutes). These improvements greatly enhanced plant biomass (46 %) and yield (31 %). Overall results proved that co-application of 2 % BC and KSB effectively enhanced K availability for sustainable plant growth. Still, there is a need to identify the most efficient KSB strains that, in conjugation with BC, reduce the K fertilizer usage.