Soil Organic Carbon Sequestration in Size-Fractions of Water-Stable Aggregates in Haplic Luvisol after Organic Amendment

Abstract

Size-fraction of water-stable aggregates (WSA), soil organic carbon (SOC) in soil bulk, and different sizes of WSA and their contributions to C sequestration were determined under different rates of biochar (B0: no biochar, B10: 10 t ha⁻¹, and B20: 20 t ha10 t ha⁻¹) at the Experimental Station of Slovak University of Agriculture in Nitra, Slovakia. The results showed that only the application of 20 t of biochar ha⁻¹ significantly reduced the content of WSAmi compared to B0. In B10 treatment, SOC in soil bulk decreased by 7%, but in case of B20, it increased by 14% compared to B0. In B20, the higher SOC content in soil bulk was also reflected in higher SOC concentration in size-fractions of WSA than in B0 and B10 treatments. However, a higher representation of SOC in WSA from the total SOC from the soil bulk was found in the B10 than in B0 and B20 treatments. SOC contents in WSAma >3 mm and 0.25-0.5 mm polynomial increased with their proportions in B0 and B10, and opposite decreased in WSAma 3-0.5 mm and WSAmi along with all treatments. These results indicated that the rate of biochar is crucial for C sequestration in soil bulk and in WSA. Water-stable macro-aggregates have a great potential for C sequestration in soils after organic amendments.