Soil health is a key factor for the global food security. One of the main bottlenecks for the efficient utilization of farmland soil is the accumulation of allelochemicals excreted by plant roots, leached and volatilized from plants, and released during the decomposition of plant residues. The negative impacts derived from allelochemicals include: decreasing soil fertility, breaking the balance of soil microbial community, reducing seed germination rate and crop yield, and interfering with the growth of neighboring or successive plants. Recently, biochar, a soil amendment with low cost and high performance, is extensively studied on its functions and effects on farmland systems. In this review, we focused on the potential role of biochar in controlling the environmental fate and risk of allelochemicals in soils. The source and potential toxicity of allelochemicals in farmland and the deficiencies in current methods for alleviating the allelopathy were summarized first, followed by the discussion on their sorption and degradation by biochar as well as the impact of biochar properties on the performance and mechanism. At the same time, the generation of allelochemicals regulated by biochar through improving plant growth conditions was analyzed. The modification of biochar for alleviating the allelopathy and then overcoming the obstacles of agricultural production was also addressed. Future research directions, such as targeted biochar production, the interactions between different allelochemicals and biochar investigated by simulations and modeling, negative effects and stability of biochar or modified biochar, were then proposed. This review will provide useful theoretical and technical supports for targeted biochar applications in soils with allelopathy. Graphical abstract

Adsorption of black peanut skin anthocyanins, a natural pigment, onto various macroporous resins was optimized to develop a potential approach for large-scale production of black peanut skin anthocyanins. Seven different macroporous resins (AB-8, SP-207, LS-305A, HP-20, LS-305, DM-21 and LS-610B) were evaluated for the adsorption properties of the anthocyanins extracted from the black peanut skins of Arachis hypogaea L. The adsorption experiment proved that compared to AB-8, SP-207 and LS-305A, four resins, i.e., LS-610B, DM-21, LS-305 and HP-20 have relatively higher capacity of adsorbing black peanut skin anthocyanins from the aqueous solution, which are verified by the related adsorption experiments. The adsorption isotherm data was successfully described by Langmuir isotherm model and the pseudo-second-order rate model simulates the kinetic process well. Column adsorption and desorption tests further proved DM-21 is a promising adsorbent for field applications to recover black peanut skin anthocyanins from aqueous solution. The overall yield of pigment product was 14% based on dried black peanut skin, and anthocyanins purity is at about 5.7% in the pigment product.

Inoculating phosphate-solubilizing microbes (PSMs) is an effective approach to increasing the soluble phosphorus content in soil for plant growth. While biochar has been shown to promote microbe growth, it can also lead to phosphate precipitation. Therefore, the specific benefits of biochar application for phosphate activation remain unclear. In this study, biochars with varying physicochemical properties were utilized as carriers for microbes. PSMs of Talaromyces pinophilus (T. pinophilus) strains were isolated from the rhizosphere soil of corn, radish, and wheat plants, with FePO₄ as the sole phosphorus source. To understand how biochar modulates the phosphate-solubilizing capacity of T. pinophilus, we measured the dissolved phosphate content, strain biomass, and the concentrations of various organic acids excreted by the strains. Our findings suggested that biochar primarily enhanced the phosphate-solubilizing ability of T. pinophilus by stimulating the secretion of organic acids, rather than by increasing strain biomass. The phosphate-solubilizing ability increased by 356% after adding corn straw biochar to the strains isolated from wheat rhizosphere soil. Notably, citric acid showed the most significant correlation with the phosphate-solubilizing ability of the strains. Laboratory-simulated experiments using individual organic acids indicated that the abundant carboxyl groups in citric acid may be a primary property contributing to phosphate release from FePO₄. This study highlights the essential role of organic acids excreted by PSMs, which are stimulated by biochar, in phosphate solubilization. These findings not only provide valuable insights for optimizing phosphate utilization in the environment but also contribute to the development of biochar-based biofertilizers, advancing sustainable agricultural practices. Graphical Abstract

Panax notoginseng is a prominent traditional Chinese medicinal herb, yet its yield and quality are significantly constrained by continuous cropping obstacles, primarily stemming from soil-related issues. This study analyzed soils subjected to various degrees of continuous P. notoginseng cultivation, soils without P. notoginseng planting, and natural forest floor soil without P. notoginseng planting. The objective was to investigate variations in soil microbial communities, physicochemical properties, and enzyme activities across different cropping conditions. Macro-genome sequencing was employed to reveal microbial shifts and key factors influencing rhizosphere microbial communities. Notably, the natural forest floor soil exhibited the highest levels of soil organic matter, soil organic carbon, total nitrogen, and available potassium. Furthermore, continuous cropping soils showed the highest levels of pH, available phosphorus, electrical conductivity, and total potassium. The activities of catalase, urease, acid phosphatase, sucrase, and soil FDA hydrolase decreased significantly after continuous cropping, but increased again after five years of fallowing. Microbial analysis revealed that Bacteroidetes, Firmicutes, and Chloroflexi dominated the soils without P. notoginseng planting, whereas Proteobacteria, Actinobacteria, and Acidobacteria were the predominant phyla in continuous cropping and natural forest floor soils. Continuous cropping led to an increase in Acidobacteria, Gemmatimonadetes, and Chloroflexi, while fallowing reduced Actinobacteria. Gemmatimonades was almost exclusively present in the continuous cropping soils. Overall, continuous P. notoginseng planting altered the soil nutrients and microbial composition. Key factors influencing microbial communities included pH, nitrate nitrogen, available phosphorus, available potassium, and electrical conductivity. The study suggests that attention should be paid to scientific and rational fertilization practices to mitigate the effects of continuous cropping. Additionally, a fallow period of more than five years is recommended. The proper application of probiotic fertilizers is also advised. Finally, cultivating P. notoginseng under forest conditions is recommended as a viable method.