EVALUATION OF NH4+ ADSORPTION CAPACITY ON GREY SOIL SPIKED BY DERIVED BIOCHAR FROM RICE STRAW

Abstract

Biochar which has the ability to improve soil fertility has received significant attention in sustainable agricultural development. Biochar affecting the N-NH4+ change in soil was recognized. Study on the characteristics of biochar derived from rice straw prepared at different temperatures and the ability to adsorb ammonium nitrogen of gray soil (Cu Chi, Ho Chi Minh City) and soil with additional biochar were performed. The treated rice straw was heated at temperatures of 300, 450 and 600 °C with the heating rate set to 10ºC per minute and a 2-hour holding time. Soil (control sample) and soil supplemented with 5% biochar were equilibrium with NH4+ solution at different concentrations. Physical and chemical properties of soil (pH, OC, NH4+ content, moisture) and bichar (recovery efficiency, OC, pH, pHpzc, H+, OH- group numbers) were collected. The results also showed that the addition of biochar to gray soil reduced NH4+ adsorption capacity. The produced biochars at lower temperatures have reducing degree less. NH4+ adsorption process followed the Langmuir isothermal model (R2 range 0.90-0.97) and Freundlich (R2 range 0.94 - 0.98), specifically, the maximum absorption capacity of NH4+ soil (control sample) and soil supplemented with 5% bichar at 300, 450 °C respectively 8.9; 3.0 and 2.7 mg /g. Therefore, it is necessary to control the amount of ammonium nitrogen fertilizer when combined with biochar to avoid excessive fertilization, causing environmental pollution and poisoning for the plants. Research results have shown the role of biochar in regulating the stability of NH4 + in agricultural production systems.
Keywords: NH4+, adsorption, straw, biochar.