Biochar is a charcoal like material derived from organic feedstock having a great potential to ameliorate arable soils, while contributing to mitigate climate change as a direct carbon sink. The porous material is proven to have beneficial impacts on physical, chemical and biological soil functions and is likely to remain in soil for hundreds of years. Biochar has been shown to improve soil quality and have positive effects on crop yield. Distinct soil microbial groups were reported to be enhanced after biochar addition. The question whether these shifts in microbial community structures depend on soil type or biochar type, or on their interaction, is open. What’s more, the extend to which microorganisms colonising biochar surfaces are responsible for its mineralization is unknown at the moment.
This project aims at investigating the effect of two biochar types on four different soils and on the soil-plant systems. Maize straw (Zea mays) and wood chips are used as feedstock for biochar production. Thanks to the artificial enrichment of the maize straw in its 13C stable isotope content, carbon decomposition and incorporation processes can be followed using the 13C abundance technique. The project will evaluate benefits and risks of crop production on soils amended with biochar and provide knowledge on the contribution of biochar to soil quality and climate change mitigation. We are interested in the way how microbes associate with biochar particles and to what extend soil biological properties are changed. The comparative analysis of various biochar-soil combinations will show whether the effects depend on biochar or soil type, or on their interaction.
Biochar has a great potential to ameliorate arable soils, especially those that are low in organic matter due to intensive use or erosion. Biochar is carbonised organic material with high porosity that brings about changes in physical, chemical and biological soil functions. Biochar amended soils show a higher water and cation exchange capacity with reduced leaching and enhanced availability of plant nutrients. The microbial biomass in biochar amended soils is enhanced and more diverse. Biochar is stabilised organic material, which is likely to remain for hundreds of years in the soil. Photosynthetically fixed atmospheric CO2 stabilised in biochar may thus act as a direct carbon sink and help to mitigate climate change. As feedstock and production conditions produce different biochar qualities predictions of effects in soil need to consider biochar and soil properties case by case. To date biochar has been approved to ameliorate highly weathered tropical soils with positive effects on crop growth and yield. Distinct microbial groups were reported to be enhanced in soils but if this depends on the particular soil or biochar or a combination of both is an open question, especially in temperate climates. Likewise, it is not known if microorganisms colonising biochar surfaces are responsible for its mineralization or if they just use the new niches provided.
The aim of the proposed project is to investigate the influence of two biochar types on soil-plant systems by determining i) soil nutrient availability, plant growth and nutrient uptake, ii) structure and function of soil microbial communities, iv) the decomposition and fate of biochar in soils. We will use two loessial soils from the well-known DOK-trial with different soil organic matter content. Other soils from the region will be selected to provide a wider range of soil quality, in particular pH. The biochars will be produced by pyrolysis and hydrothermal carbonization (HTC) from the 13C enriched maize material and unlabelled woodchips. Pyrolysis derived material has bigger pore sizes due to the evaporating gasses and is commonly alkaline, whereas the HTC derived biochar has a finer pore size, a much higher oxygen content and more acidic functional groups.
The use of 13C labelled maize as feedstock for biochar production provides the opportunity to follow decomposition and incorporation processes by the use of 13C-tracer techniques. The effects of biochar on soil microbial biomass, activity and diversity in soil will be estimated by microbial biomass (13Cmic), carbon mineralisation (13CO2), and marker molecules for microbial groups (13C-phospholipid fatty acids, PLFA). The potential toxicity of biochar on seed germination and microbial growth will be analysed by standard tests. Analysis of 13C-PLFA will allow for studying the role of specific microbial groups in the decomposition process and provides the basis for in depth analysis of actively colonizing species on biochar surfaces by fluorescence in situ hybridization (FISH) and nano-scale secondary ion mass spectrometry (NanoSIMS) imaging. The presented study will evaluate benefits and risks of soil amendment with biochar from pyrolysis and HTC, and will provide knowledge on how it contributes to soil quality and to the mitigation of climate change. We will investigate how microbes associate with biochar particles and to what extend soil biological properties are changed. The comparative analysis of biochar-soil combinations will provide evidence if effects can be attributed to a certain biochar, soil or their combination.
Coordination and conduction of the main activities
