The long-term excessive use of chemical fertilizers may result in soil degradation, but manure and straw application is considered to be an effective approach for alleviating this problem. The aim of this study is to examine the long-term impacts of different fertilization patterns on soil quality variables in a wheat–sweet potato rotation system. Four treatments were conducted in a field trial for a duration of twelve years, including (1) no fertilizer (control, CK); (2) application of mineral fertilizers (NPK) alone; (3) NPK with crop straw return (NPKs); (4) combined use of NPK and farmyard manure (NPKm). Thirteen physical, chemical, and biological soil parameters were measured. The results showed that the NPKm and NPKs significantly improved the proportion of macroaggregates (>0.25 mm) by 24.7% and 21.9% compared to the NPK alone, respectively. The proportion of microaggregates (0.053–0.25 mm) under the NPKm was 47.4% significantly higher than the NPKs. Additionally, the NPKm resulted in a 22.2% and 19.6% increase in the SOC content than the NPK and NPKs, respectively. In terms of soil-available K, the NPKs resulted in levels that were 42.1% and 49.6% higher than the NPKm and NPK alone, respectively. Long-term fertilization significantly decreased soil pH by 0.95–1.85 units compared to the control, whereas manure application could alleviate soil acidification, as shown when the pH increased by 10.6–18.7%. The NPKm and NPKs resulted in significantly increased soil pHs by 10.6% and 18.7% compared to the NPK alone, respectively. In addition, the NPKm and NPKs increased N-acetyl-β-D-glucosaminidase activity by 52.6% and 60.3% compared to the NPK alone. Determined by the minimum data set method, the NPKm treatment exhibited the highest soil quality index, followed by the NPKs and NPK. Our findings suggested that the combined use of chemical fertilizers with organic amendments proved beneficial for enhancing soil quality.

Conventional cereal production in coastal saline–alkali drylands is constrained by low productivity and soil degradation. While diversified cropping and biochar application have each been shown to enhance soil quality, the effects of their short-term integration into continuous cereal systems remain unclear, particularly regarding crop yield, soil health, and economic returns. A field experiment was conducted to compare a continuous wheat–maize rotation (W) with systems where one cycle of that was replaced by an alfalfa–sweetpotato (A) or rapeseed–soybean (R) rotation, under biochar-amended and non-amended conditions. Diversified rotations increased subsequent wheat yields by 6.6–16.2%. System A achieved 216% and 439% higher cumulative equivalent yield and economic benefit than System W, respectively. Even without biochar, A and R systems increased soil organic matter content, aggregate stability, and fungal richness by 16.3–21.0%, 20.6–26.5%, and 8.60–10.2%, respectively, compared to W. Biochar further enhanced crop yields by 6.36–16.3% and integrated fertility score by 7.78–9.01%, but its initial cost reduced profitability. Comprehensive evaluation conducted via a weighted model indicated that system A, combined with biochar, achieved the optimal balance among productivity, soil fertility, economics, and microbial diversity. These findings demonstrate that integrating “green” (diversified cropping) and “black” (biochar) strategies offers synergistic benefits for sustainable production in coastal saline–alkali drylands.

Four lactic acid bacteria (LAB) strains isolated from naturally ensiled broccoli waste were characterized, and their effects on the fermentation quality of high-moisture broccoli waste silage were studied. The four isolated strains were assessed using the morphological, physiological and biochemical tests. The four strains were added to broccoli waste at three moisture contents (90%, W0; 87%, W1; 80%, W2) and ensiled for 60 days. All strains (CB89, CB94, CB112, and CB120) grew at 15–45 °C, pH 3.0–7.0, and in 3.0–6.5% NaCl and were identified as Lactiplantibacillus plantarum by 16S rDNA sequencing. Inoculation of CB120 significantly (p < 0.05) increased lactic acid, starch, and non-structural carbohydrate content, and significantly (p < 0.05) decreased pH values and aerobic bacteria count compared with control (CK) at all three moisture contents. In conclusion, CB120 improved the fermentation quality and nutritional value of broccoli waste silage at three moisture contents and could be applied as a promising additive for high-moisture material.

Arbuscular mycorrhizal fungi (AMF) can improve plant performance, but how they coordinately influence root metabolism and associated bacterial communities in sweet potato remains unclear. Here, a pot experiment was conducted to investigate the effects of Glomus intraradices inoculation on sweet potato seedlings by integrating analyses of rhizosphere soil properties, plant growth and nutrient uptake, root metabolomics, and rhizosphere and endophytic bacterial communities using 16S rRNA gene sequencing with FAPROTAX-based functional prediction. AMF inoculation significantly increased whole-plant fresh and dry biomass, potassium concentration and accumulation, and the accumulation of starch and water-soluble carbohydrates, while no significant effects were observed on dry matter rate or plant nitrogen and phosphorus concentration. In the rhizosphere, AMF reduced soil electrical conductivity and increased organic matter content without significantly affecting pH, alkali-hydrolyzable nitrogen, available phosphorus, or available potassium. Root metabolomic profiling identified 289 differential metabolites, with enrichment of phenylpropanoid biosynthesis, glycerophospholipid metabolism, porphyrin metabolism, and nucleotide metabolism, together with broad up-regulation of lipid-related metabolites. Bacterial communities showed strong compartment specificity, with the root endosphere displaying lower alpha diversity than the rhizosphere. Higher rhizosphere bacterial Shannon diversity was observed in the AMF treatment, together with compartment-dependent shifts in bacterial community composition; enrichment of endophytic taxa such as Devosia and Niastella was detected following AMF inoculation. Functional prediction further suggested niche differentiation between rhizosphere and endophytic bacteria, together with AMF-associated shifts in carbon- and nitrogen-related functions. Overall, these results suggest that G. intraradices inoculation is associated with enhanced sweet potato growth and enhanced potassium and carbohydrate accumulation in association with coordinated changes in rhizosphere conditions, root metabolism, and bacterial community assembly.