The study is
Roy-Choudhury, A. and Venkatakrishna-Bhatt, H. Spermatogenic Inhibition by
Cichorium intybus L. Aqueos Root Suspension in Mice. Naturwissenscaften
70(1983) pp. 365-366

These two researchers from the National Institute of Occupational Health in
India tested two concentrations of chicory, 4.3g/kg and 8.7g/kg. They found
that while the lower dose was not significant in reducing testis weight the
higher dose did have a significant effect and caused degeneration of the
seminiforous tubules and the Leydig cells were atrophied. When I searched for
this article on Web of Science there were no other articles that cited this one.
The only reason why I can think that more research was not done is that the
chicory did cause a significant drop in body weight. The mice started out as
36g and in both treatment groups they dropped to 27.43+-1.0 for 4.3g/kg and
26.33+-0.9g (p<0.005) In contrast the control gained weight on average.