NITROUS OXIDE AND CARBON DIOXIDE EMISSIONS FROM AGRICULTURAL SOIL AMENDED WITH DIFFERENT TYPES OF BIOCHAR AT THREE TEMPERATURES

A laboratory experimental study was conducted to investigate the effects of different coffee waste biochar materials at three temperatures on nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) emissions from agricultural soil in Central Vietnam. Soil amended with 2% normal biochar, 2% functional biochar (with a high NO 3 -N adsorption capacity of 20 g N kg -1 ) or no addition was adjusted at 60% water holding capacity, conditioned with 100 mg N-NO 3 kg -1 dried-soil and aerobically incubated at 25 o C, 30 o C or 35 o C for 21 days. N 2 O and CO 2 emissions were measured on days 1, 3, 5, 7, 14 and 21. Results showed that the addition of normal biochar caused more CO 2 emission but less N 2 O emission compared to the functional biochar application. At 25 o C, biochar amendment had a neutral or positive effect on N 2 O and CO 2 emissions. At 35  C, biochar amendment reduced N 2 O and CO 2 emissions compared to the control. However, there was little difference in N 2 O and CO 2 emissions among biochar treatments. In addition, with increasing temperature, a positive correlation between temperature and N 2 O and CO 2 emissions with the non-biochar amendment and a negative correlation between temperature and N 2 O with the biochar treatments were observed. This is because temperature probably affects the rate of microbial processes mediating respiration and denitrification and the soil-biochar mixture’s mobilization of N