Effects of biochar amendment on soil respiration

The objectives of this study were to quantify the effects of biochar amendment on soil respiration rate and to investigate the relationship between soil temperature, moisture content and pH on soil respiration. Five rice husk biochar treatments (0, 1, 5, 10 and 20 t ha�¹) were applied on soil plots in a completely randomized design (CRD) at the experimental field of the School of Sustainable Agriculture, Universiti Malaysia Sabah (6°02' N, 116°07' E). Each treatment was replicated three times resulting in 15 sample plots, each measuring 1 m² in size. Soil respiration data were collected using an UB100 Automated Soil CO₂ Flux System (LI-Cor Inc., Lincoln, NE, USA). Soil temperature and soil moisture data were measured with a soil thermometer and soil moisture meter (SM100) respectively. Data was recorded once a week in the morning (6.00 a.m.-8.00 a.m.) and evening section (5.00 p.m.-7.00 p.m.). The soil respiration for the 1 t ha-1 and 5 t ha�¹) biochar treatments were significantly different in this study. The maximum rate of soil respiration produced from 5 t ha�¹) of biochar amendment was approximately 9.45 t CO₂ ha�¹) yr�¹. Soil temperature was positively correlated with soil respiration. Increased soil temperature enhanced the soil respiration especially above 30°C. The soil moisture showed an inverse relationship with soil respiration. Rainfall event and distribution affected the results of soil temperature and moisture and hence soil respiration. Higher rainfall increased the soil moisture content but also reduced soil respiration significantly. The 1 t ha�¹) biochar treatment increased the soil pH but the higher biochar treatments (10 and 20 t ha�¹) significantly increased soil acidity. In conclusion, the 5 t ha�¹) biochar amendment was effective in increasing soil respiration and influenced soil properties such as soil pH and moisture which will affect agriculture activities of farmers.