Chemical attributes of an Oxisol with the addition of conilon coffee straw biochar

Abstract The objective of this work was to evaluate the effects of increasing rates of biochar produced with coffee straw, at two pyrolysis temperatures, on the chemical attributes of an Oxisol cultivated with conilon coffee (Coffea canephora) and on the nutrient content of coffee tree leaves. Treatments consisted of pyrolysis at two temperatures (350 and 600 °C) and of five biochar rates (0, 5, 10, 15, and 20 Mg ha-1). The following soil chemical attributes were evaluated: pH in water; P, K, Ca, Mg, Al, H+Al, Zn, Cu, Fe, and Mn contents; effective and potential cation exchange capacity (CEC); sum of bases (SB); base (V) and aluminium (m) saturation; and N, P, K, Ca, Mg, Zn, Cu, Fe, and Mn contents in the leaves. The biochar produced at 600°C, at rates of 10 and 15 Mg ha-1, promoted a greater K release into the soil. Regardless of temperature, coffee straw biochar increased K and P availability, sum of bases, base saturation, and CEC in the soil, but did not influence macro- and micronutrient contents in the leaves. The addition of increasing rates of coffee straw biochar in the soil increases P, K, Mg, SB, CEC, and V, regardless of pyrolysis temperature.