Straw returning is an environmentally friendly method to improve soil health and agricultural productivity by reusing organic waste products. However, fields are often also treated with inorganic fertilizers, and the effect of the interaction between phosphate fertilizer application and straw return on crop yield remains unclear. Therefore, a full-factorial, two-year field experiment was conducted on sweet corn (NARC-16 in late 2021 and Kashmeri-19 in early 2022) to explore how crop yield may be optimized by combining straw return with efficient phosphate fertilization. The experiment involved the application of DAP, SSP, and NP (three different types of phosphates) and the application of crop waste byproducts, namely the residual stover left after sorghum and maize harvesting. We compared control fields with no crop waste or phosphate addition (CR0 and PS0) to experimental plots treated with various phosphates and straw return. Growth parameters such as days to emergence, tasseling, silking and maturity, emergence rate (emergence m⁻²), height of plant, number of leaves, leaf area per plant, and yield were evaluated, and the influence of the treatment on the economic value of crops was estimated. Phosphorus and straw return were applied at rates of 90 kg per hectare and 5 tons per hectare, respectively. The best P-crop straw combination treatment involved DAP (90 kg ha⁻¹) with the incorporation of 5 tons’ ha⁻¹ of maize straw, which resulted in delayed tasseling (50 days), early silking (68 days), taller plants (178 cm), improved thousand-grain weight (233 g), maximum biological yield (11,349 kg ha⁻¹) and grain yield (3760 kg ha⁻¹). The application of DAP with maize straw return resulted in the highest plant height, biological yield, and grain yield of sweet corn during the second year of the experiment, despite the first year’s yield being influenced by a natural disaster. This combined management strategy (using either DAP or crop residuals) was found to have a more a favorable cost–benefit ratio (BCR) efficiency. In conclusion, increasing the use of crop residuals can help reduce the expensive application of synthetic mineral fertilizers like SSP and NP, while significantly increasing sweet corn production and improving profit margins. Considering the importance of environmental friendliness and sustainable agriculture, the combined use of DAP and straw return is considered a viable method.

Bone meal has been used as economic and effective additive for heavy metals (HMs) pollution remediation due to the distinct components and structures that enable their favorable properties, such as its low cost, high adsorption capacity, acid-base adjustability, and ion-exchange capability. However, no attempt has been made to establish whether cow bone could promote the passivation of HMs and the removal of metal resistance genes (MRGs) and antibiotics resistance genes (ARGs) during the composting process. Two sizes of cow bone (meal (T2) and granule (T3)) were added to investigate their effects on humification, HMs passivation and the abundance of ARGs and MRGs during swine manure composting. Excitation-emission matrix (EEM)-parallel factor analysis showed that the percentage of maximum fluorescence intensity of humic-like substances were higher in T2 (91.82%) than in T3 (88.46%), implying that T2 could promote the humification process compared to T3. In comparison with control (T1), the addition of T2 and T3 could promote the change of exchangeable Cu and reducible Cu into oxidizable Cu, thus reducing the mobility factors (MF) of Cu in T2 and T3 treatments by 10.48% and 6.98%, respectively. In addition, T2 and T3 could increase exchangeable Zn into reducible Zn and oxidizable Zn, thereby reducing the MF of Zn in T2 and T3 treatments by 18.80% and 2.0%, respectively. Quantitative Real-time PCR (qPCR) analysis revealed that the total abundances of MRGs were decreased by 100% in T2 and T3 treatments, and T2 decreased the total relative abundance of ARGs. Furthermore, the relative abundance of ARGs and MRGs had significantly correlated with intI1 and bio-available of Cu and Zn, which was triggered by selective pressure of HMs and horizontal gene transfer. The present study suggested that cow bone meal as additives can be a feasible approach to promote the passivation of HMs and enhance the removal of MGRs and ARGs by decreasing horizontal gene transfer and selective pressure by bioavailable HMs.

Ammonia-oxidizing microorganisms (AOM) are vital for soil nitrogen cycling, nutrient availability, and soil health during sustainable agriculture. Long-term continuous cultivation of bananas and improper chemical fertilization affect the adaptability of AOM; however, the underlying basis for this phenomenon is unclear. This study utilized 16S rRNA gene and metagenomic sequencing techniques to examine soil from banana plantations that were continuously cultivated for 2, 3, 7, 10, 12, and 13 years (Y2, Y3, Y7, Y10, Y12, and Y13, respectively). The results indicated a significant decrease in soil acidity buffering capacity (pHBC) with increasing years of continuous cropping. Furthermore, compared with forest soil (Y0), Y7, Y10, Y12, and Y13 soils exhibited a significantly increased potential nitrification rate (PNR) as well as an abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), with no significant difference in complete ammonia oxidizers (comammox). Principal component analysis (PCA) further demonstrated marked differences in chemical properties and ammonia-oxidizing microbial community structures between the soils under long-term (Y7, Y10, Y12, Y13) and short-term (Y2, Y3) banana cultivation. In addition, metagenome analysis results indicated that the relative abundance of Nitrososphaera-AOA and Ca. Nitrosocosmicus-AOA as well as Nitrosospira-AOB, Nitrosovibrio-AOB, Nitrosomonas-AOB, and comammox Nitrospira jacus was significantly higher in Y7 and Y13 soils than in Y0 controls. Redundancy analysis (RDA) identified pHBC, CEC, and NH4+ as the primary chemical factor responsible for the differences in AOM microbial communities, whereas random forest analysis revealed that Nitrosospira-AOB significantly contributed to PNR. In summary, long-term continuous banana cultivation primarily stimulates AOB promote soil ammonia oxidation, leading to soil acidification.

The lower humification efficiency during composting is an emerging challenge that attenuates compost quality. Although biochar has the potential to enhance humification, its effectiveness is limited by factors such as its alkaline pH and the absence of functional groups. Here, Ca-modified biochar was prepared via co-pyrolysis of coconut shell and oyster shell (1:1 ratio) at 600 °C and added to pig manure composting at a 10% (w/w) dose. The result of spectroscopy analysis of the developed compost revealed that carboxyl and carbonyl functional groups facilitated the adhesion of oyster shells to the biochar surface. The addition of Ca-modified biochar in compost not only increased the concentrations of humic acid (+ 8.6%) but also improved the seed germination index (GI) (+ 18.9%) compared to the control group. The excitation-emission matrix analysis indicated that the modified biochar facilitated the transformation of protein-like molecules, thereby enhancing the humification of organic matter by 4.92% compared to the control group. Microbial analysis indicated that Proteobacteria and Bacteroidetes were predominant in the modified biochar group, exhibiting a 107% higher prevalence, as compared to the control group. These enriched microbial taxa, known for their role in lignin degradation, are inferred to inhibit nitrogen volatilization, generate precursor substances, and catalyze the conversion of organic matter into stable humus. The correlation analysis further revealed a significant positive correlation between Proteobacteria and GI ( p < 0.05). These findings demonstrated that Ca-modified biochar enhances physicochemical and microbiological processes, offering a scalable solution for improving humification and supporting sustainable compost production. Graphical Abstract