Soil quality degradation and low nutrient use efficiency constrain sustainable maize–soybean rotation in the Albic soil region of Northeast China. A field experiment was conducted in 2023–2024 at Qixing Farm (Jiansanjiang, Heilongjiang, China) to evaluate chemical fertilizer combined with cattle manure or microbial inoculants. Five treatments were established: no fertilization (CK), chemical fertilizer alone (CF), chemical fertilizer combined with cattle manure (CF+CM), chemical fertilizer combined with a Bacillus subtilis inoculant (CF+CRA), and chemical fertilizer combined with a Bacillus megaterium inoculant (CF+CRB). Soil available nutrient dynamics, crop nutrient accumulation and translocation, fertilizer use efficiency, and yield were assessed. In maize, CF+CRB significantly enhanced pre-anthesis N translocation and post-anthesis P accumulation, increasing grain yield to 14,533 kg ha⁻¹ (+28.6% vs. CF). In soybean, CF+CRB produced 3328.15 kg ha⁻¹, 15.8% higher than CF. CF+CRA significantly increased soil available P during the soybean flowering-pod stage and improved K allocation at later stages. Overall, integrating chemical fertilizer with CRB improved yield and nutrient use efficiency. Based on crop-specific nutrient requirements, CRB is recommended for the maize season to strengthen nutrient translocation, whereas cattle manure or CRA can be applied in the soybean season to sustain K supply.

Meadow albic soils in the Sanjiang Plain of Northeast China are characterized by a compact plow layer, weak structural stability, low organic matter content, and limited nutrient availability, which restrict crop productivity in maize–soybean rotation systems. A two-year field experiment (2023–2024) was conducted to compare the effects of mineral fertilizer alone (CF) and CF combined with carbon-based organic fertilizer (CF+COF), humic acid organic fertilizer (CF+HA), or biochar-based fertilizer (CF+BC) on soil properties and crop yield. Soil aggregate composition, pH, organic carbon, total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, and enzyme activities were measured together with yield and 100-grain weight. Compared with CF alone, the combined application of organic amendments generally improved soil properties and increased crop yield, although the magnitude and pattern of response differed among materials. CF+COF was more effective in increasing the proportion of medium-sized aggregates, enhancing alkali-hydrolyzable nitrogen and some enzyme activities, and achieving relatively high yields in both maize and soybean seasons. CF+HA showed comparatively balanced effects on aggregate composition and nutrient availability, whereas CF+BC was more effective in maintaining relatively high soil pH, increasing available phosphorus, and promoting larger aggregates at later growth stages. Overall, all three organic amendments combined with mineral fertilizer were beneficial for improving meadow albic soil and increasing crop yield, with CF+COF showing the best overall performance under the conditions of this study.