• Energy Research

Forest soil acidification caused by acid deposition is a serious threat to the forest ecosystem. To investigate the liming effects of biomass ash (BA) and alkaline slag (AS) on the acidic topsoil and subsoil, a three-year field experiment under artificial Masson pine was conducted at Langxi, Anhui province in Southern China. The surface application of BA and AS significantly increased the soil pH, and thus decreased exchangeable acidity and active Al in the topsoil. Soil exchangeable Ca2+ and Mg2+ in topsoil were significantly increased by the surface application of BA and AS, while an increase in soil exchangeable K+ was only observed in BA treatments. The soil acidity and active Al in subsoil were decreased by the surface application of AS. Compared with the control, soluble monomeric and exchangeable Al in the subsoil was decreased by 38.0% and 29.4% after 3 years of AS surface application. There was a minimal effect on soluble monomeric and exchangeable Al after the application of BA. The soil exchangeable Ca2+ and Mg2+ in the subsoil increased respectively by 54% and 141% after surface application of 10 t ha-1 AS. The decrease of soil active Al and increase of base cations in subsoil were mainly attributed to the high migration capacity of base cations in AS. In conclusion, the effect of surface application of AS was superior to BA in ameliorating soil acidity and alleviating soil Al toxicity in the subsoil of this Ultisol.

Biochar research has experienced a significant increase in the recent two decades. It is growing quickly, with hundreds of reviews, including meta-analyses, that have been published reporting diverse effects of biochar on soil properties and plant performance. However, an in-depth synthesis of biochar–soil interactions at the molecular level is not available. For instance, in many meta-analyses, the effects of biochar on soil properties and functions were summarized without focusing on the specificity of the biochar and soil properties. When applied to soils, biochar interacts with different soil components including minerals, organic matter, gases, liquids, and nutrients, while it also changes soil microbial community structure and their occurrence. These different interactions modify soil physicochemical properties with consequences for dynamic changes in nutrient availability and, thus, plant performance. This review systematically analyzed biochar effects on soil properties and functions: (a) soil physical properties; (b) chemical properties; (c) biological properties; and (d) functions (plant performance, nutrient cycling, etc.). Our synthesis revealed that the surface properties of biochar (specific surface area and charge) and its associated nutrient content determine its role in the soil. At the same time, the extent of changes depends on soil properties, suggesting that both biochar and soil properties need to be considered for harvesting benefits of biochar application. Altogether, we believe our synthesis will provide a guide for researchers and practitioners for future research as well as large-scale field applications.

Soil arsenic (As) contamination is a serious concern because of its mark negative impacts on plant growth and physiological processes. In plant-soil system, As competes against phosphorus (P) which depends on charge component of different soil types. The main objective of this study was to investigate the influence of ((NH4)3PO4 (PO43-) and Ca5(PO4)3(OH) (phosphorite)) in ameliorating As stress on plant physiological process against As toxicity and their role in As accumulation. We performed eighteen treatments with different levels of As (0, 35, and 70 mg/kg) and P (0, 100, and 200 mg/kg) against two P sources of PO43- and phosphorite. Overall, more improvement in plant growth was observed by addition of PO43- than phosphorite. Significant increases in plant height (51%), dry biomass (root (49%) and shoot (40%)), chlorophyll contents (88%), total soluble sugars (58%) and plant functional leaves (51%) were observed by PO43- application as compared to their corresponding un-fertilized treatment under As stress conditions. However, proline and MDA contents were decreased by 49% and 71% with PO43- applied, respectively, under As stress. The As and P uptake by soybean were remarkably enhanced by the application of PO43- than phosphorite. Therefore, highly soluble P supplementation has great potential to minimize As-induced damage to plant growth in acidic soils and improve As uptake by plants. The findings obtained in present study will be used as an important tool for amelioration of As polluted acidic soils.