Root windows – a tool to study relationships between rhizosphere processes, soil-microbial communities, and plant performance under field conditions?

Background and Aims: Root observation windows (RW) installed in the field provide a tool for non-destructive monitoring of root development and rhizosphere processes. However, the highly invasive installation process, requiring cutting of soil profiles, may affect plant development and finally the outcome of the experiments. This study systematically compares plant development with and without RW installation. Methods Using the location of a long-term field experiment, the responses of winter wheat to different intensities of tillage, N-fertilization, and use of fungicides were compared for plants grown along root windows and in undisturbed control plots. The sampling was performed during vegetative growth, six weeks after RW-installation with comparisons of shoot and root biomass, root length, mineral nutritional status, expression of stress-related genes, and the composition of microbial communities reflecting the conditions in the rhizosphere (RH). Results The presence of RW did not affect most of the parameters analyzed. As an exception, a range of mineral nutrients (K, Mg, Ca, Cu, Mn) was increased in RW plants most probably due to RW location in the border rows of the experimental plots with reduced inter-plant competition for nutrient uptake. By contrast, N-fertilization intensity and fungicide use affected plant biomass, root growth, and fungal communities. Tillage intensity mainly affected the composition of RH-microbial communities and the expression of stress-related genes in the leaf tissue. Conclusion The results suggest only a limited influence on plant performance six weeks after RW installation with plant responses and experimental results comparable to undisturbed controls.