Agronomy

To explore the effects of Fe/P-loaded biochar on neutral Cd-contaminated paddy soils and the potential synergistic effects between biochar and modifying materials, a pot experiment was conducted using neutral paddy soil with a total Cd concentration of 1.10 mg/kg. Ball milling was employed for modified biochar production. Specifically, iron-loaded biochar (PBCFe) and phosphorus-loaded biochar (PBCP) were prepared using Fe₂O₃ and K₃PO₄, respectively. Results showed that PBCP significantly increased rice biomass while effectively inhibiting Cd uptake and accumulation in rice grains. Compared to the control (CK), P (K₃PO₄), and PBC treatments, the Cd content in rice grains under PBCP treatment decreased by 69.20%, 52.13%, and 56.06%, respectively. Moreover, compared with the treatments using single modifiers, PBCP and PBCFe effectively reduced Cd uptake and accumulation in rice tissues, especially in leaves and stems. In contrast, PBCP was more effective than PBCFe in enhancing iron plaque formation and Cd adsorption onto iron plaque. This promoted Fe uptake in rice roots, which might inhibit the upward translocation of Cd from roots to stems. Further analysis with FTIR and XPS results indicated that PBCP might be more compatible in immobilizing Cd in soil by inducing Cd-P co-deposition. Therefore, phosphorus-loaded biochar (PBCP) could be a more promising amendment for remediating Cd-contaminated alkaline rice paddy soils and improving rice quality.

Although the role of proline (Pro) as an important osmolyte has been extensively studied, there are few comprehensive studies on their metabolism under salinity conditions. We investigated Pro metabolism in two habanero pepper varieties with contrasting salinity responses: Mayan Chan (tolerant) and Mayan Ba’alche (sensitive). First, a phylogenetic analysis of enzymes participating in their biosynthesis, P5CS and P5CR, and in its degradation, PDH, was performed. Additionally, the levels of their transcripts, the enzymatic activity, and Pro content were determined in plants subjected to 150 mM NaCl by short (0, 24, 48 and 72 h) and long (seven days) periods. Potassium flux in roots exposed to NaCl, in the absence or presence of Pro, was also measured. Phylogenetic analysis showed that the sequences were grouped according to their taxonomic family and not by salt tolerance of the species. Molecular and biochemical analyses showed significant differences between organs and varieties; the tolerant variety showed highest levels of transcripts, biosynthesis enzymes activities and accumulation of Pro. The results suggested that Pro metabolism in habanero pepper is a complex process, that is regulated at different levels and differentially between organs and varieties. Exogenous Pro only reduced potassium efflux in the sensitive variety exposed to NaCl, suggesting that a precise threshold of this amino acid is required to perform this function.

To clarify the effects and mechanisms of the solution formed by mixing flaxseed meal powder with water on soil water movement in sandy land, this study conducted laboratory simulation experiments using three extraction forms of flaxseed meal solution (supernatant, suspension, and precipitate) and five application rates (5 kg·m⁻², 8 kg·m⁻², 11 kg·m⁻², 14 kg·m⁻², and 17 kg·m⁻²), with untreated aeolian sandy soil set as the control (CK). The results showed that: (1) Flaxseed meal can significantly reduce the soil water infiltration rate, with the sediment treatment group exhibiting the optimal effect. After the application of the three flaxseed meal treatments, soil infiltration indices decreased significantly, and the magnitude of the reduction became more pronounced with the increase in flaxseed meal application rate. (2) Flaxseed meal exhibited a significant effect on water retention and evaporation inhibition; after continuous evaporation for 35 days following the spraying of different flaxseed meal treatments, the cumulative evaporation of CK was significantly higher than that of the other treatments. Compared with CK, the cumulative evaporation of the groups treated with the supernatant, suspension, and precipitate of flaxseed meal solution decreased by 11.69%, 24.13%, and 43.22%, respectively. The sediment group achieved the optimal effect, and the evaporation inhibition effect was enhanced with the increase in application rate. (3) All three flaxseed meal mixture treatments increased soil bulk density and decreased soil total porosity, and saturated water-holding capacity and minimum water-holding capacity, with the sediment treatment exerting the most significant effect. The efficacy of all treatments became more notable as the application rate increased. There was a highly significant correlation between soil physical properties and water movement rate. Flaxseed meal affects soil water movement by altering soil physical properties. In conclusion, spraying flaxseed meal on the surface of sandy soil can effectively reduce infiltration and inhibit evaporation, with the sediment treatment group achieving the optimal improvement effect. The soil crust formed by flaxseed meal has a strong water-binding capacity, which can maintain water supply for plant growth over a long period, making it highly suitable for popularization and application in sandy farmland.