Biochar is provided that is treated to have certain chemical and physical properties found to have the highest impact on plant growth and/or soil health. In particular, the following physical and/or chemical properties, among others, of a biochar have been identified as critical properties to control for in the selection of biomass feedstock, pyrolysis conditions, and/or enhancing treatment to increase biochar performance: (i) bulk density (ii) impregnation capacity; (iii) particle size distribution; (iv) solid particle density; (v) surface area; (vi) porosity; (vii) total porosity; (viii) ratio of macroporosity to total porosity (ix) content of residual organic compounds; (x) content of volatile organic compounds; (xii) ash content; (xiii) water holding capacity; (xiv) water retention capabilities; (xv) levels of dioxins and other potentially hazardous byproducts of pyrolysis; and (xvi) pH. Treatment can modify and preferably increase hydrophilicity/decrease hydrophobicity, remove dioxins from the raw biochar, modify electrical conductivity and/or surface charge, modify cation exchange capacity and modify anion exchange capacity, among other things.