DIRECT EFFECTS OF HUMIC-LIKE SUBSTANCE ON GROWTH, WATER, AND MINERAL NUTRITION OF VARIOUS SPECIES

Abstract

The influence of humic-like substances was studied on various crop plants (cucumber, maize, pelargonium, and wheat, for example) cultivated under hydroponic conditions. The humic-like product, called SHB®, was extracted from poplar sawdust by a thermical and mechanical process and applied diluted into nutrient solutions of soilless culture at concentrations ranging between 100 to 400 mg SHB® L−1. The application of the humic-like substance induced a biostimulating effect on plant growth of each species studied. Treated plants present a faster development and reach reproductive stage three to five days earlier than control. SHB® also provoked a better efficiency of plant water uptake and they improved the mineral nutrition. It is assumed that most of direct effects on plant metabolisms are related to the low molecular size fractions (LMS) because it is the only part of SHB® which can penetrate into root tissues. But, it is also suggested that high molecular size fractions (HMS) could participate in plant water saving by slowing down its passage in roots.