Chemical properties of Oxisols treated with humic materials from sub-bituminous coal

One way to improve soil chemical properties of Oxisols is by adding ameliorant, for instance humic substance (HS), to the soil. As there are many kinds of organic matter being a source of humic matter, to investigate a specific type of humic substance for improving the soil chemical properties of Oxisols is necessary. This research was aimed to study the capability of humic substance derived from non-productive coal (sub-bituminous) powder which was extracted with Urea, KCl, NaCl, and NaOH and then it was used to improve the soil chemical properties of Oxisols. The improvement of chemical properties of Oxisols was expected to be achieved by adding humic substance from sub-bituminous. Urea could be used to substitute the role of NaOH in solving humic materials and improving soil chemical properties of Oxisols. Humic materials which were extracted by Urea 0.2 g (kg)-1 of soil and sub-bituminous in concentration 0.5 % to improve soil chemical properties of Oxisols.