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The use of biochar in agricultural soils is currently being researched worldwide. Previous research results suggest that biochar has a positive effect on soil quality, in particular through improved soil structure, water holding capacity and nutrient sorption, as well as the potential for carbon sequestration. In order to evaluate the benefits and risks of the application, biochar needs to be tested under field conditions for long-term effects within different climate zones and soil types. Here we present first results from a long-term field experiment in Switzerland, in which we comprehensively and continuously evaluate the effects of biochar application on soil quality and crop yield. The trial consists of five agricultural fields in Zrich, Switzerland, with a total area of 10.5 ha. Soil type is mostly clayey loam and fields are managed according to organic guidelines and with reduced tillage management. We applied biochar once in spring 2021 according to 8 t/ha on half of the area according to a split-plot design. All fields are monitored continuously until at least 2027 for soil carbon (total, carbonate and pyrogenic), total soil nitrogen, pH, cation exchange capacity, aggregate stability, water holding capacity and yields. In addition, water content and penetration resistance are measured during the vegetation period. First results indicate a positive effect of biochar application on soil organic and pyrogenic carbon, however no effects on the other measured parameters. Therefore, under the given soil and climatic conditions in temperate soils biochar application may be valid to increase long-term organic carbon contents and carbon sequestration. Other propagated effects of biochar application like improved water holding capacity, cation exchange capacity and yields require higher biochar application rates to be significantly affected.
Schlichenmaier et al. (Fri,) studied this question.