Komposzt illetve műtrágya bioszén kezeléssel mutatott együttes hatásának vizsgálata karbonátos homoktalaj nedvességtartalmára és talajlégzésére | Changes in the moisture content and respiration of a calcareous sandy soil after combined treatment with biochar and compost or mineral fertiliser

The main purpose of this work was to examine the use of biochar amended with organic or inorganic nutrients to improve soil quality and to reduce the emission of greenhouse gases (GHG), especially CO ₂, from agricultural land. There are still gaps in our knowledge of how soils with different physical, chemical and biological properties are affected by the biochar added to improve soil properties. Experiments were performed on a sandy soil at the experimental station of the Institute for Soil Science and Agricultural Chemistry (MTA ATK) at Őrbottyán, where maize was sown with seven treatments in four replications. In three of the treatments the soil was treated with various doses of biochar (0.1, 0.5 and 1.0 m/m%) and a constant rate of mineral fertiliser (designated as BC0.1M, BC0.5M and BC1.0M, respectively), while in three others the above doses of biochar were supplemented with a uniform 10 t/ha rate of compost (designated as BC0.1K, BC0.5K and BC1.0K). The 7 ᵗʰ treatment was the absolute control, given no biochar fertiliser or compost (designated as K). Soil sensors were used to monitor trends in soil moisture content, while the CO ₂ emission of the soil was recorded in each treatment using samples taken from a static chamber. No significant increase in the mean annual soil moisture content was recorded in the plot treated with 1% biochar + compost compared with the absolute control. In response to rainfall events, the soil moisture content rose to the greatest extent in the plot given 1% biochar + compost, though similar values were recorded in the plot treated with 0.5% biochar + mineral fertiliser. The soil in all the treated plots dried out more quickly after rainfall events than that of the absolute control. During drier periods with little rainfall, the soil moisture content was only greater than in the control in the BC1.0K treatment, while that in the BC0.5M treatment was similar to the control value. In all the other treatments the moisture contents were considerably lower. All in all, soils containing compost responded more sensitively to rainfall, with the best water management in the BC1.0K treatment. When applied alone, the highest rate of biochar (1.0 m/m%) had no clear soil moisture-increasing effect. The effect of biochar on carbon dioxide turnover was investigated by measuring soil respiration. Differences between the biochar + mineral fertiliser or compost treatments and the control were only recorded in a few cases, so it can be concluded that CO ₂ emission did not depend on the biochar dose. The effect of biochar on soil respiration is exerted indirectly through its influence on soil moisture content; in cases where the addition of biochar led to a rise in soil moisture content compared to the control, higher values of CO ₂ emission were also recorded. This was especially pronounced when biochar was applied with compost.