MINERAL NITROGEN DYNAMICS OVER TIME INFLUENCED BY PEANUT-WASTE BIOCHAR APPLICATION IN ALKALINE SOIL

Soil fertility in arid to semi-arid regions is constrained by extreme temperature fluctuations. Soils of such regions typically have low fertility levels, nitrogen (N) availability (due to ammonia volatilization and denitrification), and soil organic carbon (SOC) content. An incubation experiment was conducted to assess how a peanut-waste biochar (PB), produced at 300°C, influences the mineral N and chemical properties of an alkaline soil. The treatments included five PB rates (control, 5, 10, 15, and 20g PB kg−1 soil) and two fertilizer rates [no fertilization without additions of N and phosphorus (P) and fertilization with addition of 120kg N ha−1 and 90kg P ha−1]. The soil was incubated for various durations (0, 14, 28, 42, and 56days). There were significant temporal shifts in the mineral form of N in the incubated soil. Following 56days of incubation under fertilization, the treatment with 20g kg−1 PB revealed soil nitrate-N and ammonium-N levels of 15.8mg kg‒1 and 21.1mg kg‒1, respectively. With no fertilization, 20g kg−1 PB increased mineral N by 2.3-fold over the treatment without PB. This increase was 2.6-fold with fertilization. After 56days of incubation, in the presence of 20g kg−1 PB, there was a 19% increase in cation exchange capacity under fertilization and a 21% increase under no fertilization, compared to the respective treatments without PB. Immediately after the PB application, SOC was significantly increased, corresponding to PB rates. However, substantial increases were observed only in treatments with 15 and 20g PB kg−1 soil. In conclusion, the addition of 15 and 20g PB kg−1 to alkaline soil significantly increased N availability in soil, demonstrating the importance of biochar for N management in agricultural soils.