CATION-EXCHANGE CAPACITY, INDUCED IN CALCAREOUS SOILS BY FERTILIZATION WITH MANURE

The influence of organic fertilization on the increase of cation exchange capacity in calcareous soils is studied. Two soils with illite and interstratified illite-montmorillonite clay fractions, respectively, were fertilized with sheep and chicken manures and submitted to culture conditions during 3 years. The evolutions of cation exchange capacity (CEC), total organic carbon (TOC), and extractable carbon (Cex) are studied. The relationships among these parameters and increases in them induced by fertilization show that in soil with low clay content (interstratified) the increases of CEC are additive but in the illitic soil some clay-humic interaction may occur accompanied by the protection of high CEC organic fractions.