Using corn stover as raw material, the adsorption mechanism of ammonium nitrogen by biochar prepared by different modification methods was studied. The biochar was characterized by Fourier transform infrared spectroscopy, surface-area analysis and scanning electron microscopy. The results showed that the adsorption of NH 4 + − N by different modified biochars confirmed the quasi-second-order kinetic equation ( R ² > 0.95, p ≤ 0.05), the adsorption isotherms of the Langmuir equation ( R ² ≥ 0.96, p ≤ 0.05). Δ G ^θ < 0, Δ H ^θ > 0 indicated that the adsorption of NH 4 + − N by different modified biochars was a spontaneous endothermic reaction. With the increase in adsorption temperature, the adsorption capacity of biochar to ammonium nitrogen increased gradually. The adsorption was monolayer adsorption and was controlled by a fast reaction. Both KOH and FeCl ₃ modified biochars significantly improved the adsorption capacity of NH 4 + − N , and the adsorption mechanism was different. The adsorption capacity of NH 4 + − N by FeCl ₃ modified biochars mainly increased the specific surface area and micropore volume. The adsorption of ammonium nitrogen after KOH modification primarily depended on the wealthy oxygen-containing functional groups. The adsorption effect of ammonium nitrogen modified by KOH was better than that of biochar modified by FeCl ₃ .

In this study, the preparation of apricot kernel shell biochar by a hydrothermal method and its adsorption mechanism for atrazine was studied by scanning electron microscopy (SEM) and infrared spectrum (FTIR) analytical techniques. The results show that the biochar prepared from the apricot kernel shell has an evenly distributed, nonaggregated carbon microsphere structure and contains a large number of oxygen-containing groups. The higher the preparation temperature is, the more functional groups exist and the better the potential adsorption performance is. The adsorption kinetics of atrazine on apricot kernel shell biochar were fitted with a quasi-second-order kinetic equation (R² ≥ 0.995, p < 0.05). The isothermal adsorption data were in accordance with the Freundlich model (R² ≥ 0.911, p < 0.05). The adsorption of atrazine on apricot kernel shell biochar includes two processes: surface adsorption and diffusion. The adsorption capacity of apricot kernel shell biochar for atrazine increases with increasing preparation temperature and decreases with increasing pH and Ca²⁺ concentration. The adsorption mechanism includes hydrogen bonding and hydrophobic interactions. Therefore, biochar prepared from apricot shells, an agricultural waste, exhibits good adsorption performance for atrazine and has a good application prospect in addressing agricultural non-point source pollution, especially in pesticide residue pollution control.

In this study, cornstalk was pyrolysed to obtain hydrochar (HC), which was used to remove mesotrione from aqueous solutions. HC characterization and batch experiments were conducted to investigate mesotrione adsorption and the underlying mechanism. The characterization revealed microspheres on the HC surface. FT-IR spectra showed that the HC contained a large number of –OH groups, C=C bonds of aromatic rings, C–H groups in aromatic rings and phenolic C–O bonds. The adsorption results showed that the mesotrione adsorption ability gradually increased as the HC preparation temperature increased. The quasi-second-order kinetic equation ( R ² ≥ 0.9860, p < 0.05) agreed well with the mesotrione adsorption process. The maximum monolayer adsorption capacity, which was obtained at pH 7 and 45°C with HC prepared at 240°C, was 3181.7 mg kg ⁻¹ with the Langmuir isotherm model ( R ² ≥ 0.9491, p < 0.05). Van der Waals and dipole forces and hydrogen bonds were inferred as the main adsorption mechanisms. HC has potential as an effective and energy-saving adsorbent for mesotrione to reduce environmental pollution.

Saline-alkali soil significantly impairs crop growth. This research employs the impacts of the modifier and water-soluble fertilizer, as well as their interaction, on the root systems of alfalfa and leymus chinensis in saline-alkali soil. The results exhibit that the hydrochar source modifier effectively enhances the root growth of both forage species. There are certain improvements in the root growth indicators of both crops at a dosage of 20 g/kg. Root enzyme activity and rhizosphere soil enzyme activity are enhanced in alfalfa, showing significant improvements in the first planting compared to the second planting. The application of water-soluble fertilizers also promotes root growth and root dehydrogenase activity. The root dehydrogenase activity of alfalfa and leymus chinensis are enhanced 62.18% and 10.15% in first planting than that of blank, respectively. Additionally, the two-factor variance analysis revealed a correlation between rhizosphere soil enzyme activity and changes in root traits. Higher rhizosphere soil enzyme activity is observed in conjunction with better root growth. The combined application of a modifier and water-soluble fertilizer has demonstrated a significant interaction effect on various aspects of the first planting of alfalfa and leymus chinensis. Moreover, the combined application of the modifier and water-soluble fertilizer has yielded superior results when compared to the individual application of either the modifier or the water-soluble fertilizer alone. This combined approach has proven effective in improving saline-alkali soil conditions and promoting crop growth in such challenging environments.

Bauhinia is a widely planted urban tree plant in tropical cities, which are frequently dwelling in a habitat exposed to inevitable streetlamp lighting. It is of practical meaning to figure out the lighting spectra that benefit nutrient utilization in corporation with a proper exponential fertilization regime. In this study, Bauhinia brachycarpa and B. variegata seedlings were cultured with exponential fertilization at the rate of 80 mg nitrogen (N) plant^-1 (N-phosphorus-potassium, 10-7-9) with an unfertilized control, and both were exposed to light-emitting diode spectra of R1BG5 (13.9% red, 77.0% green, 9.2% blue), R2BG3 (26.2% red, 70.2% green, 3.5% blue), and R3BG1 (42.3% red, 57.3% green, 0.4% blue). The R3BG1 spectrum resulted in smaller growing size and dry mass but higher nutrient concentration and root water content compared to the other two spectra. Exponential fertilization increased fresh mass for two Bauhinia species but only increased dry mass in B. brachycarpa. Compared to B. variegata, B. brachycarpa was verified to have a higher capacity to accommodate exogeneous nutrient input through exponential fertilization. The R3BG1 spectrum was recommended for the illumination in streetlamps for Bauhinia because this spectrum can promote nutrient uptake without too fast rate of growth relative to other spectra with lower red-light proportions.

Long-term intensive cultivation has degraded soil structure and reduced soil organic carbon (SOC) retention in the black soils of Northeast China. However, the processes underlying SOC accumulation under integrated soil–crop system management (ISSM) remain poorly understood. An 11-year field experiment compared farmers’ practice (FP), high-yield and high-efficiency practice (IP), super-high-yield practice (HY), and ISSM. We assessed SOC stocks, aggregate stability, organic carbon chemistry, extracellular enzyme activities, microbial carbon-use traits, microbial community composition, and microbial necromass carbon (MNC), and used partial least squares path modeling as an exploratory analysis of potential linkages. Compared with FP, ISSM increased SOC content and stock by 87.0 and 77.0%, respectively, and achieved an SOC sequestration rate of 2.8 Mg C ha⁻¹ yr⁻¹. ISSM also increased mean weight diameter and geometric mean diameter by 45.0 and 61.0%, increased microbial biomass carbon and carbon use efficiency by 205.2 and 100.0%, and decreased qCO₂ by 71.1%. Bacterial and fungal necromass carbon increased by 100.0 and 70.0%, respectively. The relative abundance of taxa operationally classified as growth-oriented also increased under ISSM. However, MNC/SOC did not differ significantly among treatments, while SOC aromaticity and hydrophobicity declined. Path analysis suggested that microbial carbon transformation was positively associated with necromass formation, whereas aggregate stability was associated with MNC and SOC retention. These results indicate that ISSM synchronously enlarged SOC and microbial necromass pools through sustained carbon inputs, efficient microbial transformation, and aggregate-mediated physical protection rather than through increased chemical recalcitrance.