EFFECTS OF COMPOST-DERIVED HUMIC ACIDS ON VEGETABLE BIOMASS PRODUCTION AND MICROBIAL-GROWTH WITHIN A PLANT (CICHORIUM INTYBUS)-SOIL SYSTEM - A COMPARATIVE-STUDY

The responses of chicory plants to amendments with natural and synthet ic surface active substances, represented by either potassium humates from compost stabilised green waste or Tween 80, are reported from a p ot trial. Results are evaluated in terms of plant biomass production a nd behaviour of soil microbial populations following different treatme nts. Amendments with humic acids stimulated vegetative growth of chico ry. They also caused significative variations in the numbers of bacter ial heterotrophs and autotrophic nitrifiers in the soil. The study sug gests that the mechanism through which humic acids affect both plant a nd soil microbes may chiefly involve enhancement of cell membrane perm eability to nutrients.