Parent rock–pedogenesis relationship: How the weathering of metamorphic rocks influences the genesis of Planosols and Luvisols under a semiarid climate in NE Brazil

Abstract The expansion of the agricultural frontier in search of new productive regions around the world has raised the attention of the scientific community to the genesis and agricultural potential of soils in regions of the planet where the dry climate limits agricultural activities. In this context, our goal was to describe if there is a direct relationship between the weathering of different metamorphic rocks and the genesis of Luvisols and Planosols in a semiarid region of Brazil, describing the implications of the genesis of these soils for their agricultural potential. For this, two Planosols profiles and three Luvisols profiles were classified, described morphologically and sampled for the development of physical, chemical, mineralogical and micromorphological analyzes. Samples of the respective parent rocks were collected for petrographic analysis and physical and chemical attributes were used in multivariate statistical analysis. The results indicate that: a) weathering of gneiss and amphibolite results in genesis of Planosols and Luvisols respectively, b) hematite was more associated with Luvisols and goethite was more associated with Planossols, and this variation in the content of iron oxides influenced some morphological attributes of these soils, c) clay formation in situ called argillation was the main process responsible for the genesis of Bt horizons in both soils, d) alterations of plagioclases, biotite and amphibole influenced the release of plant nutrients such as Ca+2, Mg+2 and K+ and e) the set of attributes analyzed led us to affirm that Luvisols have a more relevant agricultural potential than Planosols in the semiarid region studied. Our conclusions can be extrapolated to other regions of the world under similar geoclimatic conditions.