Soil contamination with potentially toxic elements (PTEs) is considered one of the most severe environmental threats, while among remediation strategies, research on the application of soil amendments has received important consideration. This review highlights the effects of biochar application on soil properties and the bioavailability of potentially toxic elements describing research areas of intense current and emerging activity. Using a visual scientometric analysis, our study shows that between 2019 and 2020, research sub-fields like earthworm activities and responses, greenhouse gass emissions, and low molecular weight organic acids have gained most of the attention when biochar was investigated for soil remediation purposes. Moreover, biomasses like rice straw, sewage sludge, and sawdust were found to be the most commonly used feedstocks for biochar production. The effect of biochar on soil chemistry and different mechanisms responsible for PTEs’ immobilization with biochar, are also briefly reported. Special attention is also given to specific PTEs most commonly found at contaminated soils, including Cu, Zn, Ni, Cr, Pb, Cd, and As, and therefore are more extensively revised in this paper. This review also addresses some of the issues in developing innovative methodologies for engineered biochars, introduced alongside some suggestions which intend to form a more focused soil remediation strategy.

Phosphorus is considered as a basic essential element for plant growth which cannot be substituted or manufactured and is, therefore, a scarce resource to ensure food security; its sound management is considered important. One of the factors that play a significant role in its management is the determination of the critical available phosphorous (P) level in soil, in order to decide whether to apply P fertilizers or not. Since several soil and plant factors affect the value of the critical available soil P, it is considered necessary to carry out special experiments, in order to determine the soil critical P value for an area and a specific crop. The purpose of the present study was to establish critical soil and plant P values for wheat. A greenhouse pot experiment was performed on seven representative calcareous soils from the Thessaly plain in central Greece. The soils were deficient in available P and so they were fertilized with various rates of P. At appropriate stages, the above-ground plant parts were harvested and analysed for basic nutrients, including P. At the same time, soil samples were also taken and analysed for available P. The Cate and Nelson technique was applied, to determine critical values of both soil and wheat tissue P values. It was found that the critical soil P is 11 mg P kg-1 and the critical value for wheat tissue is 0.24% P dry matter.