The chemical properties of the matrix mainly include pH value, conductivity value, cation exchange performance, nutrients and water quality.
pH value: The pH value of the matrix affects the form, solubility and effectiveness of the nutrients. In production, the matrix is required to have relatively stable acidity and alkalinity. Generally speaking, the pH value of the matrix should be 5.5~7.5. pH value is a scale of hydrogen ion concentration in the solution and a measure of the acidity and alkalinity of the solution.
Conductivity value: reflects the amount of soluble salt originally carried in the matrix, which directly affects the balance of the nutrient solution and the growth of the plant. Generally, the soluble salt content in the matrix should not exceed 1000 mg/kg, preferably ≤500 mg/kg.
Cation exchange performance: The cation exchange capacity (CEC value) is expressed as the number of centimoles of cations replaced by 1000 grams of matrix. Generally, 10~100 centimoles/kg is more appropriate. Cation exchange performance is an important indicator for evaluating the ability of the matrix to retain and release nutrients.
Nutrients and water quality: The quality of water is evaluated mainly in terms of alkalinity, soluble salts (or conductivity) and nutrients in the water. Usually, the accumulation of soluble salts in water, substrates, and fertilizers will prevent root development and cause root rot.