The Effect of biochar on the copper regulatory capacity in some Salah El-Din soils

Capacity and intensity curves were applied to study the condition of copper element in three soils with different gypsum content (hydrated calcium sulfate) symbolized by (G1) gypsum percentage 10%, (G2) gypsum percentage 20%, and (G3) gypsum percentage 35%. Three types of biochar prepared from plant residues were added to them: rice plant residue biochar (R), wheat plant residue charcoal (W), and corn plant residue charcoal (Z). Plant biochar was added at a rate of 1%. The samples were incubated for 100 days, then the capacity and intensity experiment was conducted in a thermally identical medium (Ca-Cu) using the Beckett method, the aim of which was to establish some thermodynamic parameters. After drawing the capacity and intensity curves, the regulatory capacity potential was calculated, as its values varied between (18315-41765) (Cmolc.Kg-1/mol.L-1)1/2. The highest values were in low-gypsum soil, adding corn residue biochar (G1z,) and the lowest values were in soil High gypsum added wheat residue biochar (G3W) As for the type of biochar, corn residue biochar outperformed the other types. As for the values of mobile copper, the ratios ranged between (-0.101-- -0.451) Cmolc.Kg-1. The highest values were in high gypsum soil added wheat residue charcoal (G3W) and the lowest values were in medium gypsum soil added corn residue biochar (G2Z). The free energy of substitution was all positively charged and its values ranged between (34.557-27.358) K.Joule. The highest values were in low gypsum soil added wheat residue biochar (G1W) and the lowest values were in medium gypsum soil added corn residue biochar (G2Z). The values of the Capon coefficient ranged between (2789-1648) (L.mol-1)0.5, the highest values were in low gypsum soil added corn residue biochar (G1z,), and the lowest values were in High gypsum soil, addition of wheat residue biochar (G3W). The research results indicated, according to the capacity and intensity law, a strong correlation between the amount of ions in the liquid and solid phases of the soil for the nine soils. The values of the determination coefficient ranged between (0.78-0.99). The values of the relative activity of copper were low, ranging between (16.042-8.780) 106- ( L.mol-1) 0.5. The values of the regulatory capacity increased in all soils, with a clear decrease in their values with the increase in the percentage of gypsum. The values of mobile copper decreased in all soils due to the addition of biochar. The free energy values were positive for all soils, indicating the absence of spontaneity in the nature of the reaction. The coefficient of Gabon was high for all soils, which means a strong correlation and low copper release. Therefore, these soils need to be fertilized with copper. biochar can also be added to soils contaminated with trace elements, especially copper, to reduce the effect of copper, its movement, and its availability in the soil contaminated with it. The type of biochar, corn plant residues, was superior to Other species in most of the studied traits.