Grassman was first to pointed me that second harvest isn't apropirate for juicing.
Than I found also in referenced literature by Wigmore and Meyerowitz that it is better to juice only the first harvest. Specially if you have deal with some cancer or cronic illness. Sometime I leave the wheatgrass or barley into seven cycle after the first harvest. But these plants I found suitable for enema liquid ( diluted with distilled water ). For drinking shots I follow grassman's and Dr. Ann Wigmores hints in her books: only first harvest and after that soil into decomposing procedure. And after that I prepare new cycle with clean plates and fresh soil.