Soil respiration, pH and EC as influenced by biochar

Biochar application to agricultural land is gaining significance as a strategy for C sequestration and improving soil health and nutrient cycling. Variable results have been reported for the effect of biochar on CO 2 evolution. This study was planned to assess the influence of biochar application on soil respiration (CO 2 evolution), soil pH and electrical conductivity (EC) in a silty clay loam soil during lab incubation experiments for a period up to 50 days. Surface soil sample (0-15 cm) was collected from a garden which had been used for growing vegetables for the last many years. The experiment was comprised of four treatments viz., 0, 5, 10 and 20 t biochar ha -1 . The samples were incubated at 28 o C and taken out for CO 2 measurements after 2, 5 and 10 days and for EC and pH after 0, 5, 10 and 50 days of incubation periods. The rate of CO 2 evolution increased significantly with biochar application. During the first 2 days of incubation, the rate of CO 2 evolution increased by 13.1% with 5 t, 22.4% with 10 t and 34.6% with 20 t ha -1 biochar over control treatment. The corresponding increases in CO 2 evolution were 12.8% with 5 t, 23.3 % with 10 t and 22.1% with 20 t ha -1 of biochar during 5 days, and were 14.3% with 5 t, 30.4% with 10 t and 19.6% with 20 t ha -1 of biochar over control during 10 days of incubation period. Almost similar trend was observed for cumulative CO 2 production. The soil EC and pH were also significantly greater in biochar than in the control treatment during all incubation periods. Although biochar application increased CO 2 evolution, the %C evolved from added biochar C decreased with increasing levels of biochar as it was 1.74 % with 5 t, 1.66% with 10 t and 0.82% with 20 t ha -1 of the added biochar C during 10 days of incubation period. These results suggested that biochar application increased soil respiration, EC and pH, however, the ratio of the CO 2 evolved to total biochar C generally declined with increasing levels of biochar.