SELECTIVE INHIBITORS OF GERMINATION OF LEGUME SEEDS IN ACTIVATED-SLUDGE COMPOST

Water extracts of the compost produced from activated sludge and coffe e residue were found to be selectively inhibitory to seed germination of some legumes. Germination rate of white clover (Trifolium repens L. ), red clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.) seeds were reduced to 2, 29 and 73% of the control, respectively, by water extracts of the compost (20 g l(-1)). However, the extracts did not show any inhibition to seed germination of sorghum (Sorghum bicolo r Moench), African millet (Eleusine coracana Gaertn.), and Komatsuna ( Brassica rapa L.) at the same concentration. The inhibitors in the com post extracts were separated by ion-exchange chromatography and revers e-phase high performance liquid chromatography (HPLC) and the inhibito ry activities of seed germination were tested with white clover seeds. Five inhibitors were isolated and identified as 3,4-dichlorophenylace tic acid (3,4-DCP), 3,4-dichlorobenzoic acid (3,4-DCB), 3,4,5-trichlor ophenylacetic acid, 3,4,5-trichlorobenzoic acid and mono-2-ethylhexylp hthalate by H-1-, C-13-NMR spectroscopy and mass spectrometry. The inh ibitory activities of some authentic chemicals of the inhibitors and t he related compounds were compared. The results indicated that the mai n inhibitor in the compost could be 3,4-DCB, which was contained at th e concentration of 6.58 mg kg(-1) compost and showed the strongest inh ibitory effect on seed germination of white clover among the tested co mpounds.