Retención de sulfatos en suelos de Costa Rica

Abstract

In view of the recent importance being given sulfur in the subbumid and humid tropics an exploratory study was conducted fo determine sulfate retention capacities of different sulfate levels in 30 surface Costa Rican soils. The different sites were selected to give a wide range in environmental conditions and soils although the study was not specific for any given area. When the different soils were equilibrated with 2500 ug S/g soil, amounts of sulfur retained varied from 340 to 1260 ug S/g of soil. The sulfate retention curves correspond to the type II as described by Brunaner, indicanting multimolecular retention; however, nine soils gave a better fit to Langmuir isotherms and 21 were better explained by Freundlich isotherms. A positive test for alofane in most cases corresponded to those soils which fit Langmuir isotherms. Sulfate retention was positively correlated with organic matter contents (r=0.62), iron (r=0,39++), and aluminium oxides (r=0.48) and negatively correlated with the sum of cations (r=0.54++) and with the exchangeable Ca (r= —0.54++), all significant at the level of P<0.01, however no relations was found with pH and clay content.