Split-root labelling to investigate N rhizodeposition by Pinus sylvestris and Picea abies.

We investigated the transfer of N into the soil via N uptake and release by tree roots, which involves the principles of the split-root technique. One half of the root system received an injection of (NH)SO and the other half equivalent amounts of (NH)SO at N natural abundance level. N was transferred from one side of the root system (N side) to the other side (N side) and released into the soil.