The potential for biochar application in "Shatangju" (Citrus reticulate cv.) orchard on acid red soil: Biochar prepared from its organic waste in an orchard

A 2-year pure biochar addition enhances soil carbon sequestration and reduces aggregate stability in understory conditions

The enhancement of soil aggregate size and stability is crucial for mitigating climate change and improving carbon sequestration in forest ecosystems. Biochar, derived from rice husks, has been suggested as an effective mean to increase soil carbon storage. However, isolating biochar's specific effects on soil aggregate formation and carbon sink capacity can be complex due to the overlapping influences of fertilization and understory vegetation cultivation. Our study circumvented these variables by incorporating different amounts of biochar into plantation soil without any additional cultivation or fertilization, conducting a detailed two-year field experiment. The findings revealed that biochar significantly increased the organic carbon content and density in the uncultivated under-forest Ferralsols, thus enhancing its carbon sink function. Intriguingly, while biochar raised the proportion of small soil aggregates (< 0.25 mm) and their organic carbon levels, it decreased the fraction of larger aggregates (> 0.25 mm), adversely affecting soil aggregate stability. These results suggest that biochar may compromise soil aggregate structure and stability in the absence of plant growth. The positive impact of biochar on soil carbon storage was found to depend more on its inherent inert carbon content than on soil type. Moreover, biochar alone was insufficient to increase the quantity of soil macroaggregates without the binding action of plant root exudates. Biochar's key function appears to be in enhancing the soil aggregate-forming processes facilitated by plant roots and microorganisms. Therefore, for optimal carbon sequestration in forest soils, integrating biochar application with appropriate agricultural practices is advisable.

Distinct toxic effects, gene expression profiles, and phytohormone responses of Polygonatum cyrtonema exposed to two different antibiotics

The excessive usage of veterinary antibiotics has raised significant concerns regarding their environmental hazard and agricultural impact when entering surface water and soil. Animal waste serves as a primary source of organic fertilizer for intensive large-scale agricultural cultivation, including the widely utilized medicinal and edible plant, Polygonatum cyrtonem. In this study, we employed a novel plant stress tissue culture technology to investigate the toxic effects of tetracycline hydrochloride (TCH) and sulfadiazine (SDZ) on P. cyrtonema. TCH and SDZ exhibited varying degrees of influence on plant growth, photosynthesis, and the reactive oxygen species (ROS) scavenging system. Flavonoid levels increased following exposure to TCH and SDZ. The biosynthesis and signaling pathways of the growth hormones auxin and gibberellic acid were suppressed by both antibiotics, while the salicylic acid-mediated plant stress response was specifically induced in the case of SDZ. Overall, the study unveiled both common and unique responses at physiological, biochemical, and molecular levels in P. cyrtonema following exposure to two distinct types of antibiotics, providing a foundational framework for comprehensively elucidating the precise toxic effects of antibiotics and the versatile adaptive mechanisms in plants.

Biochar and organic fertilizer drive the bacterial community to improve the productivity and quality of Sophora tonkinensis in cadmium-contaminated soil

Excessive Cd accumulation in soil reduces the production of numerous plants, such as Sophora tonkinensis Gagnep., which is an important and widely cultivated medicinal plant whose roots and rhizomes are used in traditional Chinese medicine. Applying a mixture of biochar and organic fertilizers improved the overall health of the Cd-contaminated soil and increased the yield and quality of Sophora. However, the underlying mechanism between this mixed fertilization and the improvement of the yield and quality of Sophora remains uncovered. This study investigated the effect of biochar and organic fertilizer application (BO, biochar to organic fertilizer ratio of 1:2) on the growth of Sophora cultivated in Cd-contaminated soil. BO significantly reduced the total Cd content (TCd) in the Sophora rhizosphere soil and increased the soil water content, overall soil nutrient levels, and enzyme activities in the soil. Additionally, the α diversity of the soil bacterial community had been significantly improved after BO treatment. Soil pH, total Cd content, total carbon content, and dissolved organic carbon were the main reasons for the fluctuation of the bacterial dominant species. Further investigation demonstrated that the abundance of variable microorganisms, including Acidobacteria, Proteobacteria, Bacteroidetes, Firmicutes, Chloroflexi, Gemmatimonadetes, Patescibacteria, Armatimonadetes, Subgroups_ 6, Bacillus and Bacillus_ Acidiceler, was also significantly changed in Cd-contaminated soil. All these alterations could contribute to the reduction of the Cd content and, thus, the increase of the biomass and the content of the main secondary metabolites (matrine and oxymatrine) in Sophora. Our research demonstrated that the co-application of biochar and organic fertilizer has the potential to enhance soil health and increase the productivity and quality of plants by regulating the microorganisms in Cd-contaminated soil.