Excessive application of phosphorus (P) fertilizers does not alleviate P deficiency in soils and may cause water eutrophication. The available P in acidic soils is bound to minerals, such as iron and aluminum, in forms that are difficult to utilize by plants. The low availability of P is detrimental to soil health and crop growth. To address the P imbalance in the soil, different bioremediation techniques, such as phosphate-solubilizing bacteria (PSB) application, have been employed. However, the systematic analysis of the effects of composite inoculation of PSB on crops remains elusive. In this study, the effects of composite-inoculated PSB on plant growth were systematically evaluated by two scales: plate experiment and soil test. This study employed six different strains of PSB including Lelliottia amnigena 1-1 (A), Kluyvera intermedia 1-2 (B), Pseudomonas tolaasii 1-6 (C), Burkholderia cepacia 2-5 (D), Pseudomonas frederiksbergensis 2-11 (E), and Pseudomonas rhodesiae 2-47 (F). Among the 57 different combinations of these strains, four combinations (AE, AF, ADF, and AEF) indicated higher phosphate-solubilizing abilities than the single strains. These combinations were used for subsequent experiments. The plate experiment revealed that composite strains were more effective than single strains in promoting the growth and development of seedlings and roots of oilseed rape. Furthermore, AE, AF, and AEF combinations indicated excellent growth-promoting effects. Moreover, the soil test revealed that the composite inoculation of AE and AEF significantly enhanced biomass accumulation and root development in oilseed rape. The increased growth-promoting effects of the composite strains were observed to be associated with to their phosphate-solubilizing capacities. Both scales confirmed that compared to single inoculation, composite inoculation of PSB is more beneficial for plant growth. This study provides composite inoculation materials and foundational data to support the bioremediation of P imbalance in soil.

Intensive pig production systems in China face dual challenges of heavy metal (HM) contamination and nutrient overloading from manure. However, stage-specific quantitative relationships between diet and excretion remain poorly characterized, hindering targeted mitigation. To address this, we conducted a comprehensive farm survey in the southern water network region—a major pig production hub in China—collecting 93 paired feed and manure samples from piglets, finishing pigs, and sows across 32 large-, medium-, and small-scale farms. The results revealed that essential trace elements (Cu, Zn, Fe, Mn) in feed exceeded safety guidelines by 3–19-fold, while toxic metals (As, Hg, Pb, Cd, Cr) remained below hygienic limits. Notably, Cu and Zn concentrations in manure significantly surpassed organic fertilizer standards, with piglet manure showing the highest exceedance rates (69–91%). Strong linear correlations (Pearson’s r = 0.360–0.766) were found between feed additives (Cu, Zn, As, Pb, Cd, Cr) and their excretion in manure, with Cu and Zn exhibiting the strongest relationships, especially in piglets. Feed crude protein (CP) and phosphorus (P) levels positively influenced nitrogen (N) and P excretion (r = 0.389–0.860), particularly in finishing pigs. Scenario analysis demonstrated that aligning Cu and Zn supplementation with safety guidelines could reduce HM excretion by 50–67%, while low-CP diets and precision P feeding lowered N and P losses by 10.2–10.8% and reduced feed costs by 4.1%. These findings highlight the potential of dietary interventions to mitigate environmental risks without compromising productivity, offering actionable strategies for sustainable pig production and revised feed regulations. This study provides quantitative, stage-specific evidence linking feed formulation to excretion patterns, addressing critical knowledge gaps in feed-to-manure transfer mechanisms and supporting the development of precision feeding standards and integrated manure management systems to decouple livestock intensification from environmental degradation.

Sustainable manure recycling in cold climates faces low efficiency and nutrient loss. This study evaluated housefly larva-pretreated manure (HL) for winter swine manure composting in East China, comparing it to sawdust-conditioned (CK2) and untreated manure (CK1). Larval pretreatment converted 12.71% of manure weight into biomass, assimilating 10.69% C, 30.55% N, 8.54% P, and 11.53% K. Harvested larvae contained 53.35% crude protein, with amino acids matching/exceeding fishmeal and soybean meal, while heavy metals were below safety limits. Theoretical annual larval protein yield per unit area (29,530 kg·mu⁻¹·year⁻¹) was 206.5 times higher than soybean crops. During composting, the HL treatment promoted early protease and catalase activation. This enzymatic synergy accelerated organic matter degradation and maturation, achieving a germination index of 147.67% by day 51. Coordinated nitrate and nitrite reductase activity in HL facilitated efficient denitrification, minimizing NO₂⁻ accumulation and N₂O emissions. Consequently, HL composting achieved faster stabilization, enhanced nutrient retention, and greater protein recovery compared to controls. These findings demonstrate that housefly larval pretreatment offers a climate-resilient and scalable strategy for winter manure management and protein valorization, with strong potential for applications in cold and resource-limited agricultural systems worldwide.