Relationships between Soil Chemical Properties and Soil Structure in Soil after Initial Application and Reapplication of Biochar and Its Combination with N Fertilization

Abstract

ABSTRACT The effects of biochar application on soil properties have been widely discussed in the literature. As its effect is known to weaken over time, its reapplication may be beneficial in ameliorating the soil properties, including soil structure, however, there are several knowledge gaps. Therefore, this work addresses the effects of initial biochar application (0, 10, 20 t ha−1) and its reapplication (0, 10, 20 t ha−1) alone and in combination with N fertilization (40–240 kg N ha−1) on the relationships between the chemical properties of the soil and soil structure in silty loam Haplic Luvisol (Slovakia) during 2017–2019. Results showed that initial application as well as reapplication of biochar improved soil structure, however, more pronounced changes were observed after biochar reapplication when compared to its initial application. In both cases, most of the soil structure parameters were more favorably affected by the application of biochar alone than by its combination with N fertilization and at a higher rather than a lower rate. Due to the initial application of biochar and its reapplication, the stability of the soil aggregates was significantly supported by increasing soil pH and improvement of the soil sorption capacity, while Fe and Al oxides did not improve soil structure.