N transfer in three-species grass-clover mixtures with chicory, ribwort plantain or caraway

Summary

Background and aims
There is substantial evidence that legume-derived Nitrogen (N) is transferred to neighboring non-legumes in grassland mixtures. However, there is sparse information about how deep rooted nonlegume forage herbs (forbs) influence N transfer in multi-species grasslands.
Methodology
Red clover (Trifolium pretense L.) was grown together with perennial ryegrass (Lolium perenne L.) and one of three forb species: chicory (Cichoriumintybus L.), ribwort plantain (Plantago lanceolata L.) or caraway (Carum carvi L.) in a field experiment. During the first year after the establishment, red clover leaves were labeled with 15N-urea to determine the N transfer from red clover to companion ryegrass and forbs.
Results
On an annual basis, up to 15 % of red clover N was transferred to the companion ryegrass and forbs, but predominantly to the grass. The forb species did not differ in their ability to take up clover N, but biomass production and soil N acquisition was higher in chicory and plantain than in caraway.