In order to establish the influence of humic substances (Carbovit) on phosphorus, bases exchanges and microelements of a Molisol, greenhouse essays were penormed at the College of Agriculture of the National Universityof Colombia located in Santafe de Bogota, during the second semester of 1992. The experiment was taken into plastic vases using com (Zea mays L.) as an indicator plant until sixty days after sowing. Resutts show that the humic acid molecule acts as a transport of solouble fertilizers appliedto the soil. Besides, elements like phosphorus, iron, magnesium and zinc showed increased levels of those elements in solution in to the soil. It was also found an equilibrium activity among bases relation ship, altributed to the humic acid molecule.