EFFECT OF NKP FERTILIZER ON CHEMICAL AND MINERALOGICAL PROPERTIES OF 3 GALICIAN SOILS (NORTHWESTERN SPAIN)

In order to study the effect of NPK fertilizers, the properties of the solid and liquid phases of natural and fertilized topsoils, developed from granite, slates and gabbro, were compared. For granite and slate topsoils, soil solution pH, soils pH and base saturation were higher in fertilized samples, while the opposite accured for that of gabbro. In all three cases fertilization caused a decrease in total Al in solu tion; in gabbro and granite topsoils there was an increase in inorgani c Al precipitation while, in slated topsoil, echangeable Al increased. Hydroxy-Al interlayered 2:1 phyllosilicates behaved more similarly to vermiculites in fertilized topsoils.