Biochar application to sandy soil: effects of different biochars and N fertilization on crop yields in a 3-year field experiment

During the past years, most biochar studies were carried out on tropical soils whereas perennial field experiments on temperate soils are rare. This study presents a 3-year field experiment regarding the effects of differently produced biochars (pyrolyzed wood, pyrolyzed maize silage, hydrothermal carbonized maize silage) in interaction with digestate incorporation and mineral N fertilizer application on soil C and N, crop yields of winter wheat, winter rye and maize and the quality of winter wheat. Soil C and plant available potassium were found to be significantly positive affected by pyrolyzed wood biochar whereas the latter only in combination with N fertilization. Crop yields of winter wheat, winter rye and maize were not affected by biochar and showed no interaction effects with N fertilizer supply. Wheat grain quality and nutrition contents were significantly affected by biochar application, for example, highest amounts of phosphorus, potassium and magnesium were determined in treatments amended with pyrolyzed maize silage biochar. Biochar induced an improved availability of plant nutrients, which apparently were not yield limiting in our case. These results limit the potentials of biochar for sustainable intensification in agriculture by increasing crop yields for the temperate zones. However, detection of other environmental benefits requires further investigations.