Investigations of respiration, fertility and nutrient retention of soils in relation to charcoal addition and soil management.

Soil carbon fractions resistant to decomposition are interesting both for the global heating issue (carbon sequestration) and the agricultural community (soil fertility and carbon sequestration). My present study concerns two research areas within the common area of resistant soil carbon - addition of stable carbonic charcoal to arable soil on one hand, and effects of soil management on carbon mineralization, i.e., CO₂ emission, on the other. Addition of charcoal will increase the soil carbon pool, and soil management will influence the fluxes in and out of this pool. The study will also to a great extent address other questions than just carbon fluxes. An evaluation of the use of charcoal as a soil additive must include investigations of its influence on decomposition in soil, effect on nutrient retention and soil fertility, stability of the charcoal in soil, differences between different types of charcoal and also the possible toxicity of the additive. Investigations of the effects of soil managements on respiration are based on the common observation that soil tillage accelerates decomposition rates, and aim at clarifying the mechanisms behind this effect, possibly in terms of substrate exposure, changed soil water content, drying/rewetting cycles etc. Both these parts of my study will also require methodological development, and in particular, I will use a multi-channel respirometer in both parts of the study. This equipments measures carbon dioxide evolution from soil samples using chemical (KOH uptake of CO₂) and electrical (measuring resistance proportional to CO₂ uptake) technology. I will possibly modify existing equipment for my needs, particularly for investigating the effects of stirring/shaking the soil on decomposition rates. I will also cooperate with other researchers as much as possible, e.g., on microbial kinetics during decomposition and even microscopical investigations of the effects of stirring.