The present invention provides a method of producing a pelletized composition containing leonardite, sedimentary rock and gypsum. The method calls for pre-mixing the humic substance and the sedimentary rock for at least two weeks to yield a developed mixture prior to addition of other materials such as gypsum and pelletizing and drying the pellets to produce the final product. The invention also includes several pelleted compositions containing leonardite, rock phosphate and gypsum. In one aspect of the invention the rock phosphate comprises a mixture of sedimentary rock phosphate and igneous rock phosphate. In another aspect of the invention, the igneous rock phosphate comprises carbonatite and the sedimentary rock phosphate comprises phosphorite.