Co-application of biochar and cattle manure counteract positive priming of carbon mineralization in a sandy soil

Abstract

Background: Application of biochar has been suggested as a carbon (C) management strategy to sequester C and enhance soil quality. An incubation study was carried out to investigate the interactive effect of biochar and cattle manure application on mineralization of carbon (C) in a tropical coastal savanna sandy soil. Methods: The soils were amended with three sole levels of cattle manure (0, 13 and 26 tons ha-1) or biochar (0, 20 and 40 tons ha-1) and four combined manure–biochar levels (20 or 40 tons ha-1 biochar plus 13 or 26 tons ha-1 manure) and CO2 evolution was measured over 56 days incubation period. The soils were analyzed for mineral N (NH4+-N and NO3--N) and water extractable organic C, and net N mineralization, and priming effect (PE) values calculated. Results: The cumulative C mineralized increased in the sole manure and biochar amended soils, resulting in 45–125% positive PE. However, co-application of biochar and manure decelerated decomposition of C, probably through adsorption of labile C and net N immobilization, subsequently leading up to negative 35% PE. Conclusions: The results suggest that co-application of biochar and cattle manure can potentially stabilize C in manure amended sandy soils, albeit with a temporary mineral N limitation to plants