EFFECT OF MESQUITE ON DYNAMICS OF PHOSPHO RUS

The effect of mesquite (Prosopis sp.) on phosphorous dynamics has been studied in this paper. The work was carried out in three areas: grass land, native forest and selected clearing. The samples were collected under mesquite trees and in open sites covered by natural grasses. Pho sphorous adsorption isotherms were drawn and the following indices obt ained: maximum adsorption (Xm), affinity (K) and sorption (S). General ly, these soils show low affinity and low maximum phosphorous adsorpti on, as in other sandy soils studied. The soils taken from under trees presented higher affinity and lower maximum adsorption than those from between trees or open areas. This situation is more noticeable in the two contrasting areas: under native forest and natural grassland, the indices shows intermediate values at the sites of selected clearing.