Although agronomic recommendations for raising the pH of organic substrates are consolidated, little information is available for its reduction. The increasing use of alternative raw materials, however, makes it necessary to develop methods for decreasing pH, since some materials with good physical and biological properties are alkaline and are not recommended for the majority of species. The objective of this research was to determine the efficiency of elemental sulfur (S0) in decreasing the pH of an alkaline substrate, and evaluate a method to calculate the dose to be added. It was evaluated the mixture of five doses of S0 to a commercial substrate compound of composted eucalyptus bark (0, 4, 8, 12 and 16g S0 dm-3 substrate), based on its neutralizing value (NV). The pH and electrical conductivity (EC) of the substrates were assessed. The S0 is effective in reducing the pH of organic substrates, but it causes increases in EC. The NV of the substrate is a reliable criterion for guiding the determination of the S0 dose to be added.
plants propagation; horticultural substrates; nutrition; neutralizing value.
