Science et changements planétaires / Sécheresse


Degré d’aridité, dynamique du calcium et pédogenèse en Inde péninsulaire Volume 5, issue 3, Septembre 1994

Cirad, Institut Français de Pondichéry BP 33 Pondichéry, Inde
  • Page(s) : 185-90
  • Published in: 1994

Red fersiallitic soils cover vast expanses of the crystalline shield of southern India. Their formation is explained more by the lack of deep drainage (estimated by water balance calculations, its median value is nil) than by low rainfall. The calcium dynamics related to the rare occurence of years with positive deep drainage enables two pedogenesis pathways to be distinguished: one, calcimorphic, generating soils with calcretes, the other, acidic, corresponding to decalcified soils. To reach the well-developed profiles that may be seen today, these pedogeneses must have taken place over a long time under climatic conditions with little variation. The dryness at the bottom of the profiles is the corollary or relatively satisfactory water availability in the upper horizons. It is this availability of water, associated with the positive agronomic characteristics of the fersiallitic soils, which makes the southern Indian red soil regions relatively fertile and, on occasions, allows for two crops a year.