Biochar as a strategy to sequester carbon and increase yield in durum wheat

Carbon sequestration in agricultural soils is a climate change mitigation option since most of cultivated soils are depleted of soil organic carbon and far from saturation. The management practices, most frequently suggested to increase soil organic carbon content have variable effects depending on pedo-climatic conditions and have to be applied for a long time periods to maintain their sink capacity. Biochar (BC), a carbon rich product obtained through carbonization of biomass, can be used for carbon sequestration by applying large amounts of carbon very resistant to decomposition. The BC remains into soil for a long time and there is evidence that the BC stores atmospheric carbon from centennial, to millennial timescales. However most of the agronomic studies on BC application have been made in tropical and sub-tropical climates, while there is a substantial lack of studies at mid-latitudes and in temperate climates. This paper presents the results on an investigation of large volume application of BC (30 and 60 t ha−1) on durum wheat in the Mediterranean climate condition, showing the viability of BC application for carbon sequestration on this crop. BC application also has positive effects up to 30% on biomass production and yield, with no differences in grain nitrogen content. Moreover no significant differences between the two BC treatments were detected, suggesting that even very high BC application rates promote plant growth and are, certainly, not detrimental. The effect of the biochar on durum wheat was sustained for two consecutive seasons when BC application was not repeated in the second year.

Research highlights
► Biochar application to soil could be a viable option for carbon sequestration.
► Durum wheat yield is increased by biochar application and its quality maintained.
► Converting agricultural residues to biochar is a method to reduce CO2 emissions.