Eugene Balashov

The effect of biochar on the properties of a loamy sand Spodosol with different fertility level in the ploughed horizon has been studied in a 60-day laboratory experiment. It has been found that the application of biochar resulted in a significant increase of the soil water content in the range of soil-water potential from −5 to −50 kPa, a significant decrease of the total shrinkage of the soil with high level of fertility after three wetting-drying cycles, and the accumulation of a significantly higher content of nitrates in the soil. At a water content of 21%, less favorable conditions for the denitrification development were formed in the soil with high level of fertility than in the medium-fertile soil, which resulted in lower cumulative N2O emission from the former. The addition of biochar resulted in no significant changes in the cumulative emission of CO2 from the studied soil but significantly reduced the emission of N2O from the soil at the simultaneous addition of biochar and clover residues.

Since biochar is considered to be a significant source of carbon, in this work we have evaluated the changes in soil organic matter (SOM) and soil structure due to application of biochar and biochar with N fertilization, and have considered the interrelationships between the SOM parameters and the soil structure. The soil samples were collected from Haplic Luvisol at the locality of Doln Malanta (Slovakia) during 2017. The field experiment included three rates of biochar application (B0 -no biochar, B10 -biochar at the rate of 10 t ha -1 , B20 -biochar at the rate of 20 t ha -1 ) and three levels of N fertilization (N0 -no nitrogen, N160 -nitrogen at the rate of 160 kg ha -1 , N240 -nitrogen at the rate of 240 kg ha -1 ). The rate of biochar at 20 t ha -1 caused an increase in the organic carbon (C org ) content. The combination of both rates of biochar with 160 and 240 kg N ha -1 also caused an increase in C org .

Soil water-stable aggregation is an important process for carbon sequestration and is a key factor controlling soil sustainability and resilience; therefore, the objectives of the present study were to (1) evaluate the differences in soil organic matter state, its specific and labile fractions and their importance in the formation of water-stable aggregates in vineyard soils differing in their genesis and texture under different soil management (vineyard rows – tilled and grassed in-between strips), and (2) estimate the ability of the vineyard soils to sequester soil organic carbon (SOC) into water-stable macro-aggregates (WSAma). The results showed that the WSAma content of the soils ranged from 47% to 97%. Soils with grasses had a higher SOC and labile carbon (CL) contents than the bulk soil and, as a result, the higher total WSAma content. Soils ranged in a decreasing order in their ability to sequester SOC and CL from bulk soil to WSAma: Haplic and Stagni-Haplic Luvisols > Calcaric Fluvisol = Rendzic Leptosol > Haplic and Luvi-Haplic Chernozem > Dystric and Eutric Cambisols. Our results showed that the maximum ratio of SOC content in WSAma to that in bulk soil was 1.0 at the maximum WSAma content regardless of the soil type. An increase in the ratio above this threshold value (1.0) resulted in a decrease in WSAma content.