The content of WSAma with fractions mm decreased with time. On the contrary, the content of WSAma with particle sizes above 5 mm increased with time in all treatments except the B10N2 and B20N2 treatments. A statistically significant trend was identified in the proportion of WSA in the B10N2 and B20N2 treatments, which indicates that biochar with higher application levels of N fertilizer stabilizes the proportion of water-stable aggregates. | Vietnam Journal of Earth Sciences, 40(2), 97-108, Doi: Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences (VAST) Soil structure and soil organic matter in water-stable aggregates under different application rates of biochar Vladimir Simansky1*, Jan Horak2, Martin Juriga1, Dusan Srank1 1 Department of Soil Science, FAFR - SUA Nitra, 949 76 Nitra, Tr. A. Hlinku 2, Slovak Republic Department of Biometeorology and Hydrology, HLEF - SUA Nitra, 949 76 Nitra, Hospodarska 7, Slovak Republic 2 Received 3 November 2017; Received in revised form 11 January 2018; Accepted 13 February 2018 ABSTRACT The effects of biochar and biochar combined with N-fertilizer on the content of soil organic matter in water-stable aggregates were investigated. A field experiment was conducted with different biochar application rates: B0 control (0 t ha-1), B10 (10 t ha-1) and B20 (20 t ha-1) and 0 (no N), 1st and 2nd levels of nitrogen fertilization on silt loam Haplic Luvisol (Dolna Malanta, Slovakia), in 2014. The N doses of level 1 were calculated on required average crop production using balance method. Level 2 included additional 100% of N in year 2014 and additional 50% of N in year 2016. The effects were investigated during the growing seasons of spring barley and spring wheat in 2014 and 2016, respectively. Results indicate that the B20N2 treatment significantly increased the proportion of water-stable macroaggregates (WSAma) and reduced water-stable micro-aggregates (WSAmi). Aggregate stability increased only in the B20N1 treatment. The B20N2 treatment showed a robust decrease by 27% in the WSAma of mm. On the other hand, an increase by 56% was observed in the content of WSAma with fractions 3-2 mm compared to the B0N0 treatment. The effect of N fertilizer on WSAma was confirmed only in the case of the B10N2 treatment. The proportion of WSAma with fractions 3-2 mm decreased by 42%, .
