Roots in the surroundings of biopores

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To date, the role of the subsoil for nutrition of arable crops is in dispute because on the one hand the prerequisites for nutrient uptake in the subsoil are generally adverse and root-length densities in the subsoil are generally low, whereas on the other hand, at least under certain environmental conditions, crops can take up large proportions of nutrients from the subsoil. The surroundings of biopores have probably a key function as hot spots for root growth in the subsoil. Whereas the roots growing through the lumen of pores much larger than their own diameter are at least partly exposed to air and have limited access to the resources of the pore wall, roots growing through the surroundings of biopores can establish root-soil contact more easily and draw benefit from high concentration of nutrients, microbiological activity and facile access to water and oxygen. This project will focus on investigation of root growth in the surroundings of biopores with advanced sampling techniques. The overall hypotheses of this project are that in the surroundings of biopores - chemical and physical soil properties are influenced by the activities of anecic earthworms (deposition of feces rich in N) and plant roots (creation of fine pores by lateral roots).- root length density is greater than in the bulk soil.- root architecture in terms of diameter and branching is different from roots growing in the bulk soil.- metabolic activity of roots as indicated by mapping of pH gradients in the rhizosphere in combination with isotopic labeling is increased.Experiments will be carried out under controlled conditions in soil columns and in the field. The project will take into account that individual properties of biopores depend on their formation history, i.e. the former activity of earthworms and roots. Microcosm experiments with pores differently influenced by roots and earthworms will be established. Root-length densities will be quantified by image analyses. Metabolic activity of roots will be quantified with isotope tracers using 99 atom% 13C-urea applied with the leaf labelling technique. After cultivation, 13C release will be quantified with mass spectroscopy. Moreover, pH sensitive planar optodes will be used for mapping of pH gradients around roots growing through surroundings of biopores and the bulk soil. Suberin contents, in the biopore sheath as markers of old roots will be analyzed with gas chromatography.