Biomass-derived chars as soil amendments for sustainable agricultural management

The application of biomass-derived chars in soil amendment has revealed as a promising strategy as a bio-stimulant aimed to futuristic agriculture. Despite the good performance, the rationalization of the mechanisms and the influence of biochars properties upon driving such performance is far from been achieved. In this review we analyze the impact of the application of biochars and related biomass-derived carbons in agriculture soil management, with a focus on the characteristics of the biochars including the pH, ash content, macronutrients contents (mainly N,P,K), surface area, electron conductivity, cation exchange capacity, and the dose of biochars. Interesting results were found for some of these variables. As an attend to normalize the influence of the biochars properties upon different types of crop yields, an increase factor was introduced and up to 72 values were correlated with the dose of biochars. In addition, the effects of the crop type, irrigation, type of soil on crop yields in presence of biochars are also discussed, as well as the effect of biochars on density and microbial contents of soil. Thus, we do believe the quantity of data and the variety variables included in this review are statistically acceptable to stablish a proper assessment about the influence of using biochars as a sustainable amendment for agriculture management. A critical discussion is presented raising the importance of providing a detailed characterization and analysis of the biochars to understand the impact of their application on different crops at various stages of the seasonal crop cycle.