TEMPORAL VARIATIONS IN SOIL CHEMICAL PROPERTIES AND NUTRIENT AVAILABILITY IN RESPONSE TO MAIZE BIOCHAR PRODUCED AT DIFFERENT TEMPERATURES

Biochar is a carbon-rich material produced through pyrolysis of biological material under controlled conditions. An incubation experiment was carried out in a calcareous soil to determine the temporal effect of maize biochar produced at three different temperatures 300, 400, and 500°C on soil chemical properties and nutrient availability. The variations in potassium (K), phosphorus (P), mineral nitrogen (MN), ammonium-nitrogen (NH4 + -N), nitrate-nitrogen (NO3 − -N), soil organic carbon (SOC), cation exchange capacity (CEC) and pH was evaluated by adding biochar in soil @ 0, 1.0 and 1.5% for incubation period (10, 20, 30, 40 and 50 weeks). Results revealed that soil pH was decreased with biochars (B300 and B400), particularly @ 1%. At the end of incubation, CEC was increased (12%) over control with B300 added @ 1%. The SOC and K contents significantly increased by increasing pyrolysis temperature, biochar rate and incubation time. The highest increase in SOC (51%) and K (367%) was observed with B500 @ 1.5% over control. The N contents (NH4 + , NO3 − ) increased with increasing incubation time; highest NH4 + -N (97%) and NO3 − -N (118%) were observed @ 1.5% B300. Likewise, MN increased (107% over control) @ 1.5% B300. The available P increased in first 30 weeks but after that, it was decreased with increase in time. However, an increase of 65% in P over control was observed @1.5% B300. It is concluded that addition of B300 @ 1.5% improved the soil chemical properties and nutrient availability of the calcareous soil that needs to be verified further in field experiments.