Plant-soil feedback (PSF) is recognized as an important mechanism shaping plant communities and determining plant abundance and coexistence. Under natural conditions, plants affect the outcome of plant-soil interactions simultaneously by conditioning the soil by living roots and by litter inputs into the soil. However, most experimental studies only focus on one of the pathways, which limits our understanding of PSF in the field. 

Here, we simultaneously explored the effect of soil conditioning by living roots and of root and shoot litter addition on the performance of seven Impatiens species grown in a two-phase garden experiment. 

Soil conditioning negatively affected plant performance and the effect was at least partly explained by nutrient depletion. Root litter addition affected plant performance negatively and the results suggest that biotic effects such as pathogen transmission via the root litter played a role. The effects of root litter addition were more pronounced in control soil which, contrary to the conditioned soil, supposedly did not accumulate pathogens during the conditioning phase. Shoot litter addition increased soil nutrient levels, but had no impact on plant performance. However, presence of shoot litter aggravated the negative effects of root litter, probably due to increased amounts of nutrients available for soil biota and thus their faster growth and intensified effect on the plants. 

Overall, our study suggests that root and shoot litter have contrasting roles in plant-soil interactions and understanding their separate and interactive effects together with effects of soil conditioning is crucial for assessing the complexity of PSF.

We explored the effect of soil conditioning by living roots and of root and shoot litter addition on the performance of seven Impatiens species grown in a two-phase garden experiment. Here, we provide data on soil chemistry and plant performance in the second experimental phase. For more details about collecting and processing data, please refer to the Method section of the publication (Aldorfová et al. 2022, Oikos, 10.1111/oik.09025).